Is WiFi Calling worth it? Pros, cons and who it suits

Is WiFi Calling worth it, and should you turn it on?

For most people the answer is yes, turn it on. WiFi Calling lets you make and receive calls on your usual number where mobile signal does not reach but Wi-Fi does, and it keeps working when you are abroad. Most of its drawbacks show up only when the Wi-Fi is poor, or when you expect it to replace mobile signal completely.

WiFi Calling (technical name VoWiFi) is not a separate app. It is a feature of your normal Phone app that sends the call over the internet into your carrier's IMS system, the same core that handles VoLTE. The person you call sees your normal number, and you can reach landlines and people who have no messaging apps. That is the key difference from LINE or WhatsApp calls, where both sides need the same app.

In Thailand, Apple lists AIS, dtac and True as supporting both VoLTE and Wi-Fi Calling on iPhone, and NT Mobile runs its own WiFi Calling (VoWiFi) service. The condition that applies everywhere: your SIM must be a number the carrier has enabled for the service, and your phone must actually show that carrier's WiFi Calling setting.

Start with the basics: what is WiFi Calling?

WiFi Calling pros and cons at a glance

Look closely at the list and almost every drawback comes from the Wi-Fi you are on or from carrier conditions, not from the feature itself. So whether WiFi Calling is good for you depends mostly on where you will use it, not on the technology.

Who is WiFi Calling good for?

People whose home or office has weak mobile signal

This is the group that gains the most. If you get one bar at home, calls break up, or you walk to the window every time the phone rings, but the home Wi-Fi works well, turning on WiFi Calling often fixes it straight away without buying any equipment. AIS itself positions the service for high-rise buildings and condos where signal does not reach.

Condo dwellers, basement rooms and closed buildings

Condos with heat-reflective glass, rooms in the middle of a building, shops in a mall basement and steel-framed factories often block mobile signal more than you would expect. If there is building or shop Wi-Fi, WiFi Calling helps you avoid missing calls from customers or couriers. One catch: some shared building Wi-Fi restricts ports or needs a web login, and WiFi Calling will not come up on it. A router in your own unit is more reliable in that case.

Thai travellers going abroad

Abroad, WiFi Calling lets your Thai number make and receive calls over hotel or café Wi-Fi without attaching to a foreign roaming network. That matters for calls from your bank, family or a delivery company. AIS and True-dtac advise turning on Airplane Mode first, then connecting to Wi-Fi and waiting for the WiFi Calling indicator before you dial, so the call does not go out over roaming without you noticing.

Most travel eSIMs, including esimonline's, are data-only with no phone number. The WiFi Calling you use is therefore your home Thai SIM's (AIS, True or dtac), not the eSIM's. If you want the Thai number to ride on the eSIM's mobile data instead of Wi-Fi in a dual-SIM phone, it can work in principle, because WiFi Calling only needs an internet path to the carrier's gateway. No Thai carrier has an official page confirming this setup, though. Pantip users report it working on iPhone with AIS and dtac but not with True, so test it before you depend on it.

Set up WiFi Calling before you travel abroad

People with two numbers, or who take calls on iPad and Mac

Apple states that on a dual-SIM iPhone, if your other number's carrier supports Wi-Fi Calling, you can answer calls to that number while you are on a call on the first one; without it, that call goes to voicemail. And with Allow Calls on Other Devices turned on, you can make and take calls from an iPad or Mac signed in to the same Apple Account, which helps if you work with the phone out of reach.

Who should not rely on WiFi Calling alone?

WiFi Calling is a good backup, but it should not be your only way to make calls. These groups should always keep another route.

• Older people or patients living alone who may need to call an ambulance: if the power goes out or the router freezes, WiFi Calling stops at once. Make sure there is a spot at home with mobile signal, or keep a landline as backup.
• People on public Wi-Fi or dorm Wi-Fi shared by many rooms: at busy times audio breaks up or lags, and some of these networks block WiFi Calling entirely.
• People who take long calls on the move, in a car or walking about: leave the Wi-Fi range and the call may drop if the phone cannot hand it over to VoLTE.
• People using grey-import phones or foreign-region firmware: the setting may not appear at all, because the carrier configuration is tied to the phone's model and region.
• Travellers waiting for an OTP or a critical call: test WiFi Calling and SMS reception while still in Thailand, and have a plan B, such as switching roaming on briefly or using your bank's other verification method.

Receiving OTPs and SMS while abroad

Is WiFi Calling safe, and can you use it on public Wi-Fi?

Technically, WiFi Calling is designed on the assumption that Wi-Fi cannot be trusted. Under the 3GPP standard, the phone builds an IPsec tunnel to a carrier gateway called the ePDG, authenticating with IKEv2 and EAP-AKA using the secret key stored in your SIM. All voice and messages run inside that tunnel, so someone on the same Wi-Fi cannot simply listen in the way they could with unencrypted traffic.

What public Wi-Fi can still see is the metadata around it: that your phone is connecting to a mobile carrier's gateway, and how much data is moving. The more common risk is therefore not someone tapping the call but fake hotspots named after a café or hotel, which are usually used to trick you into typing passwords on web pages, not to attack WiFi Calling. Once the call leaves the ePDG, it travels inside the carrier's network like any normal call.

• Prefer known, password-protected Wi-Fi, such as your home router or the room Wi-Fi your hotel gave you a password for, over open networks anyone can join.
• Never type banking passwords into a page that pops up when you join public Wi-Fi; that is the real risk, not the call itself.
• A VPN is not needed for WiFi Calling, which is already encrypted, and some VPNs stop it from registering. If the indicator disappears with a VPN on, try turning the VPN off.

Does WiFi Calling drain the battery?

Apple, Samsung and the carriers publish no official figure for how much battery WiFi Calling saves or costs, and the real effect depends on signal conditions. The rule that holds: a phone burns the most battery when it has to work hard to hold on to a weak signal.

• Weak mobile signal, strong Wi-Fi: calling over Wi-Fi usually spares the phone from straining for a tower, so the battery should not drain faster than before.
• Weak or patchy Wi-Fi: the phone keeps switching between Wi-Fi and mobile and rebuilding its tunnel, and that is what makes the battery drop quickly.
• Abroad with Airplane Mode on and Wi-Fi connected: the phone stops searching for roaming networks, which takes load off the mobile radio.

If the battery seems to drop unusually fast after you turn WiFi Calling on, check whether you are somewhere the Wi-Fi keeps dropping, move the router closer, or tell the phone to forget weak public networks. Switching WiFi Calling off is rarely worth it, because you also lose the benefit in dead zones.

Why your battery drains faster abroad

Can you make emergency calls over WiFi Calling?

Apple explains that iPhone always uses the cellular network for emergency calls when it is available. If WiFi Calling is on and there is no cellular service at all, emergency calls might use WiFi Calling. The phone may share its location to help responders, but the carrier may use your registered address instead, which is why you are asked to enter or confirm an emergency address when you turn the feature on, and should keep it current.

In practice, location from a Wi-Fi call is less precise than location from the cell network, and a power or broadband outage takes WiFi Calling down. In a real emergency, move to a spot with mobile signal if you can, call 191 (police) or 1669 (emergency medical) in Thailand, and always say your address clearly out loud.

What to know about emergency calls abroad

How does WiFi Calling compare with normal calls and LINE calls?

The table shows WiFi Calling does not replace LINE or WhatsApp; they do different jobs. LINE suits free calls with people who have the app. WiFi Calling suits calls that need your real number, from a bank, hospital, courier or anyone without the app. Always check charges with your carrier: NT states that outgoing calls are billed at normal package rates and incoming calls are free, while other carriers depend on the package.

Does WiFi Calling cost money? Charges by carrier

Should you leave WiFi Calling on, and how do you set it up to get the most out of it?

Yes, leave it on: the phone uses Wi-Fi only when it makes sense, and Google notes that when you are not on Wi-Fi, calls go back to the mobile network by themselves. The steps below get you the benefits and avoid most of the drawbacks. Menu names vary slightly by model and carrier.

1. 1Turn WiFi Calling on while you are in ThailandiPhone: Settings > Cellular (Mobile Data) > Wi-Fi Calling > turn on Wi-Fi Calling on This iPhone (on dual SIM, pick the number first). Pixel: Settings > Network & internet > SIMs > choose the SIM > Wi-Fi calling. Samsung: Phone app > three-dot menu > Settings > Wi-Fi calling. AIS customers on Android may need to register first by dialling *399*1#.
2. 2Confirm your emergency addressIf the phone asks for an address, enter the one where you actually spend most of your time, and update it when you move.
3. 3Make one real test callTurn on Airplane Mode, switch Wi-Fi back on alone, wait for the WiFi Calling indicator, then call a friend. If it connects, your number is enabled.
4. 4Pick good Wi-Fi for callsUse your home router or password-protected room Wi-Fi. If the phone keeps joining weak public Wi-Fi, or Wi-Fi that blocks WiFi Calling, forget that network so the phone falls back to mobile signal.
5. 5Before travelling, sort out both data and your numberLeave the Thai SIM's WiFi Calling on, turn off data roaming on the Thai SIM, and set up a data eSIM for everyday use. If you want to try letting the Thai number use the eSIM's data, test it on your first day at the destination.

See data eSIMs for your trip

The verdict: is WiFi Calling good for you?

• Turn it on for sure if your home or condo has weak signal but good Wi-Fi, you work in a basement or closed building, or you travel and need to take calls on your Thai number.
• No harm leaving it on: if your mobile signal is already good, the gain is small, but there is no clear downside, and on a dual-SIM iPhone you can answer your second number mid-call.
• Do not rely on it alone for emergency calls, if you live alone and may need help, or if public Wi-Fi is all you have.

How WiFi Calling differs from VoLTE