True Wi-Fi Calling: how to turn it on, set it up and check it works

How do you turn on True Wi-Fi Calling?

You turn it on in your phone's settings; there is no add-on package to buy. On iPhone, go to Settings > Cellular > Wi-Fi Calling and switch it on. On Android, go to Settings > Connections > Wi-Fi Calling, switch it on for the True number and choose "Wi-Fi Preferred". The key conditions are that the number has passed the identity check the NBTC requires, and that you do this while you are in Thailand.

WiFi Calling, technically VoWiFi, means making and receiving calls on your own True number while the voice travels over Wi-Fi internet instead of the mobile tower. The phone builds an encrypted IPsec tunnel over Wi-Fi to a True network element called the ePDG, then registers with the same IMS core that carries VoLTE, as defined by 3GPP. The person you call sees your normal number, and no extra app is needed.

TrueMove H once offered this through a separate app, WiFi Calling by TrueMove H, which needed a True ID account. Today it is native: built into the phone's own dialler. If you find an old article telling you to download an app, skip it. The steps here follow what True-dtac describes on its current help page.

New to WiFi Calling? Start with the basics

Which True numbers can use WiFi Calling, and do you need to verify your identity?

True-dtac's help page says the service is available on both prepaid and postpaid. It also carries an important line: the NBTC requires identity verification to request the service, and you should bring the SIM card and your original ID card to a True or dtac shop to confirm the request. The reason is that VoWiFi places calls from a real mobile number anywhere there is internet, so the regulator wants numbers using it tied to a verified person, to make them harder to use for call-centre scams.

In practice, if your number has long been registered to your own ID card (especially postpaid), the switch usually turns on straight away. Problems tend to show up on prepaid numbers, numbers registered by someone else, or numbers whose owner details do not match. Several Pantip users describe the toggle failing until they verified at a service centre, and some needed more than one visit, so sort this out several days before you travel.

Which phones support True Wi-Fi Calling?

True has no single page listing every supported model. Its help page simply says the phone must support WiFi Calling and be on the latest software. For iPhone, the clearest confirmation is Apple's carrier features page, which lists both True and dtac in Thailand as supporting VoLTE and Wi-Fi Calling on iPhone. Apple states Wi-Fi Calling works on iPhone 5c or later with a supported carrier, which covers practically every iPhone still in use.

On Android it depends on both the model and the firmware. The phone needs a carrier configuration for True before the menu appears. Most recent Thai-market Samsung, OPPO, vivo, Xiaomi and realme phones have it, but grey imports or phones running another country's firmware (for example a Samsung whose CSC is not THL) may show no menu at all even when the hardware supports VoWiFi. For iPad, Apple's iPad carrier page does not list Wi-Fi Calling for any Thai carrier, so a True number on an iPad does not get WiFi Calling the way an iPhone does.

See which phones support WiFi Calling

How do you set up True Wi-Fi Calling on iPhone?

True-dtac's page gives a generic path, "Settings > Connections > WiFi Calling", but on iPhone the real menu sits under Cellular, as Apple documents. Names can differ slightly between iOS versions (iOS 18 and iOS 26) and display languages; some phones say Mobile Service or Mobile Data instead of Cellular.

1. 1Update iOS and carrier settingsGo to Settings > General > Software Update, then open Settings > General > About and wait a few seconds. If a carrier settings update is available, a prompt appears.
2. 2Open the Wi-Fi Calling menuGo to Settings > Cellular > Wi-Fi Calling. On a dual-SIM iPhone, tap the True line first, then find Wi-Fi Calling for that line.
3. 3Turn on Wi-Fi Calling on This iPhoneSwitch it on and tap Enable in the confirmation. You may be asked to enter or confirm an address for emergency services.
4. 4Test with Airplane ModeTurn on Airplane Mode, switch Wi-Fi back on, join a stable network, wait for "Wi-Fi" to appear after the carrier name, then make one test call. This matches the sequence True-dtac recommends.

How do you set up True Wi-Fi Calling on Android and Samsung?

For Android, True-dtac's steps are Settings > Connections > Wi-Fi Calling, switch it on for the number you want (physical SIM or eSIM), then choose "Wi-Fi Preferred". That path matches Samsung One UI 6 to One UI 8. Other brands name the menu differently but the idea is the same.

• Samsung (One UI 6–8): Settings > Connections > Wi-Fi Calling, or Phone app > three dots > Settings > Wi-Fi Calling. You can also add a Quick settings tile.
• Google Pixel and stock Android (Android 14–16): Settings > Network & internet > SIMs > pick the True number > Wi-Fi calling, per Google's help page.
• OPPO, realme, Xiaomi, vivo: usually under the SIM cards & mobile networks menu > pick the SIM > Wi-Fi calling. Exact names vary by model and version, so typing "Wi-Fi calling" into the settings search box is quicker.
• If the phone offers modes, pick "Wi-Fi Preferred", not "Cellular/Mobile Preferred". The latter only uses Wi-Fi when there is no mobile signal.

If there is no WiFi Calling menu at all, check three things in order: is the software fully updated; have you restarted the phone with the True SIM inside (carrier configuration usually loads at boot); and is VoLTE active for the number? VoLTE and VoWiFi share the same IMS core, so when VoLTE is not working, WiFi Calling usually is not either.

WiFi Calling menu missing? Fixes here

How do you check that True Wi-Fi Calling is working?

A switched-on toggle does not prove it works. What matters is that the phone has registered with IMS over Wi-Fi, which shows up as an indicator on screen. The most reliable test is to cut the mobile signal entirely with Airplane Mode: if you can still call, the call is definitely going over Wi-Fi.

1. Turn on Airplane Mode, then switch Wi-Fi back on and join your home or office network.
2. Wait 10–30 seconds. On iPhone, "Wi-Fi" appears after the carrier name when you open Control Center. On Android you get a phone-with-Wi-Fi-waves icon or a "Wi-Fi calling" label in the notification shade.
3. Call another Thai number, such as a family member, talk briefly, then have them call you back to test incoming calls.
4. Send one SMS to see whether texts go through over Wi-Fi. True's setup page does not mention SMS, so test it yourself.
5. Android users who want detail: dial *#*#4636#*#* in the Phone app, open Phone information > three dots > IMS Service Status, and see whether Voice over WiFi is registered. This works on many models, not every brand.

If you have done all this and no indicator appears, do not assume it works. Try another network first, such as a hotspot from a second phone, because some office and public Wi-Fi blocks UDP ports 500 and 4500, which the IPsec tunnel to the ePDG needs. If it fails on other networks too, the problem is usually the number's entitlement, not the Wi-Fi.

Does True Wi-Fi Calling cost money, and how is it billed?

True-dtac states plainly that charges are the same as a normal phone call at your current package rate. So there is no sign-up or monthly fee, but it is not free either: outgoing minutes come off your package just like calls over the tower, and prepaid numbers are charged from the balance at the rate of the plan you are on. The actual per-minute rate depends on your own package; True does not publish a separate WiFi Calling rate.

The Wi-Fi data side is small: the commonly quoted estimate is about 0.5–1 MB per minute of voice (an estimate, not a True figure). If you want to reach people abroad without call charges, apps like LINE or WhatsApp are cheaper because they only use data, but they do not use your True number and cannot receive bank OTP texts for you.

How much data does WiFi Calling use?

How do you use True Wi-Fi Calling abroad?

This is the main reason Thai people search for True WiFi Calling: to take calls and call home on their usual number while travelling, without turning on roaming. True-dtac sets three conditions: WiFi Calling must be switched on while you are in Thailand and never turned off; Airplane Mode must stay on while you are abroad; and you must be on stable Wi-Fi. The same page warns that some free Wi-Fi abroad does not support WiFi Calling and suggests using a hotspot shared from another phone instead.

1. 1Before you go: verify and test in ThailandGet WiFi Calling switched on and complete at least one successful test call in Airplane Mode. If it will not turn on, visit a True shop with the SIM and your ID card before you fly.
2. 2Cancel call forwardingTrue-dtac recommends dialling ##002# to cancel call forwarding (such as forwarding to voicemail), to avoid unexplained charges while you are abroad.
3. 3Boarding: switch Airplane Mode on and leave itTurn Airplane Mode on before leaving Thailand, as True-dtac specifies, so the SIM never attaches to a roaming network when you land.
4. 4On arrival: join Wi-Fi and wait for the indicatorSwitch Wi-Fi on (Airplane Mode stays on), join the hotel network and get through its login page. Wait for "Wi-Fi" or the WiFi Calling icon before every call. If it never appears, try a hotspot from another phone.

Can True WiFi Calling ride on a travel data eSIM?

Most travel eSIMs, esimonline's included, are data-only with no phone number, so calls on your Thai number still depend on the True SIM's WiFi Calling. The question is whether, in a dual-SIM phone, True's WiFi Calling can run over the other eSIM's mobile data. The straight answer: True has no official page supporting that setup, and in a Pantip thread where users compared the three carriers, AIS was reported to work but True was reported not to. The route that fits True's own conditions is real Wi-Fi, such as hotel Wi-Fi or a hotspot shared from a second phone that holds the eSIM.

Full guide to WiFi Calling abroad

True and dtac have merged: is WiFi Calling different for dtac customers?

dtac and True amalgamated into a new company, True Corporation Public Company Limited, on 1 March 2023. Since then, help content for both brands has moved to true.th. The WiFi Calling setup page this article relies on is titled True-dtac and uses the same steps for both brands, while dtac.co.th's old WiFi Calling page now redirects to a general network page on true.th.

• Setup steps, identity check and billing: the same, per the True-dtac page.
• You can verify at either a True shop or a dtac shop.
• On iPhone the carrier name still shows as True or dtac, and Apple's carrier page still lists them separately; both support VoLTE and Wi-Fi Calling.
• Call centres still use separate numbers: True customers call 1242, dtac customers call 1678.

WiFi Calling guide for dtac numbers

True Wi-Fi Calling won't turn on: what to try before calling 1242

True users usually hit one of two problems. Either the menu is missing from the phone, which is a device or software issue, or the menu is there and the toggle turns on but no indicator appears, or a message asks you to verify your identity, which is an entitlement issue on the number. Work through this order:

1. Check the number can make and receive ordinary calls and is not suspended or out of credit (prepaid).
2. Update the software and carrier settings, then restart the phone.
3. Make sure VoLTE/4G is on for the True line and mobile data is on, as True's conditions require.
4. Switch WiFi Calling off and on again, try a different Wi-Fi network, and turn off any VPN for a moment.
5. iPhone: if it still fails, Apple suggests Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings (saved Wi-Fi passwords are erased).
6. If the phone asks for identity verification, or nothing above brings up the indicator, take the SIM and original ID card to a True or dtac shop and ask staff to confirm VoWiFi is provisioned on the number.
7. Still stuck: call True Call Center on 1242 (dtac customers: 1678), say you have verified but VoWiFi still will not register, and give your phone model and software version.

True-dtac's page also says the company may suspend VoWiFi under NBTC measures without prior notice if it detects abnormal use. If WiFi Calling that used to work suddenly stops and nothing changed on the phone, ask the call centre whether VoWiFi has been suspended on your number.

WiFi Calling not working? All fixes