Điện thoại của tôi kết nối vào mạng chậm hơn

Điện thoại kết nối vào tín hiệu mạnh nhất, không phải lúc nào cũng là mạng nhanh nhất. Hãy dùng chọn mạng thủ công để thử một mạng đối tác khác, và kiểm tra chế độ mạng ưu tiên là 5G/LTE chứ không phải 3G hay chế độ tiết kiệm pin làm giới hạn tốc độ.

Seeing a network name appear in the status bar does not mean you are on the fastest network available in that spot. Every phone is built to pick whichever network gives the strongest signal exactly where you are standing at that moment, not necessarily the network with the highest download speed or the widest spectrum allocation. Those two things sometimes line up and sometimes do not. This page explains why the phone chooses the way it does, what manually selecting a network actually changes, and what else is worth checking before concluding that a slow connection is purely a network-choice problem.

It suits anyone who notices the connection feels slower than expected after eSIM installation completes, anyone who sees several partner network names listed and is unsure which to pick, and anyone wondering whether settings like the 5G/LTE preferred-network mode or a battery-saving mode genuinely affect speed. Everything here is a general principle that applies to most phones, not a specific speed figure or network name tied to any one country, since that genuinely depends on the supplier, the device, and your destination country.

Why the phone picks the network that feels 'slower'

A phone's radio is programmed to prioritise signal strength above almost everything else, because the system's first goal is keeping you connected at all, not necessarily getting you the fastest possible connection. If one network has a tower closer by but running an older generation of technology, the phone may still pick that network because its signal is stronger right now, even though a slightly more distant network on the same list would have delivered better download speed.

In many countries, a traveller's eSIM plan connects through more than one partner network rather than a single fixed one. The exact list and number of partner networks vary by country and by each plan's own supplier. Your phone automatically decides which partner to attach to based mainly on the signal it can see at that location — there is no guarantee the one it picks is the fastest of the available options.

What manual network selection actually does

Manual network selection opens a list of the networks the phone can currently see at that location, letting you pick one directly instead of leaving the choice to the automatic algorithm. The feature exists on most iOS and Android phones, but that does not guarantee every partner network on your plan will show up in the list — some phones only display networks with signal strong enough to register at that moment.

If switching to a different network manually genuinely feels faster, that tells you the network the phone had picked automatically was not the best option at that particular spot. But that result is tied to exactly where you were standing at that moment. Move to a different part of the same city, or to another city altogether, and the network that was fastest before may no longer be the best choice at all.

Where the network selection menu sits (varies by device)

The exact location of the manual network selection menu varies by phone brand, model, and operating system version. We cannot state one fixed menu path that applies to every phone, since each manufacturer lays out its settings differently, and even different versions of the same operating system sometimes move the menu from where it sat before.

The most reliable route is to search for 'network selection', 'carrier', or 'network' inside your own phone's settings search box. This menu usually sits inside the section for the specific SIM line, under the eSIM's own mobile data settings, rather than under the phone's general settings.

After manual selection, should it be switched back to automatic?

Once a network has been selected manually, the phone will not automatically hop to a different one on its own, even if the chosen network's signal drops badly, because manual selection forces the phone to keep trying to hold onto that specific network until it is switched back to automatic. This is the single most common reason travellers suddenly lose signal entirely after changing hotels or moving to a new city.

Preferred network mode: 5G/LTE versus 3G

Separate from network selection entirely is the preferred network mode setting, which determines which generations of technology the phone is even willing to connect with. If it is set to 3G Only, or has been unintentionally restricted to an older mode, the phone will never connect over 4G or 5G at all, no matter how capable the chosen network genuinely is in that area.

Check that the network mode for the eSIM line is set to something like 5G/LTE Auto or Automatic, not 3G Only or LTE Off, since some phones default to a more restricted setting than expected, particularly right after installing a fresh eSIM profile or after an operating system update.

Battery-saving modes and speed limits

Battery-saving modes on many phones automatically cap mobile data speed to extend battery life. The result can feel like a slow connection even when the network actually attached to has nothing wrong with it at all. Some travellers get in the habit of switching this on when the battery runs low mid-trip, then simply forget to switch it off again once fully charged.

If the connection still feels noticeably slow even once the battery is fully charged and heavier apps still will not run normally, check the battery-saving mode before suspecting the network itself, since it is a far quicker and easier cause to rule out.

The recommended sequence when the connection feels slower than it should

1. 1Turn off any battery-saving mode firstSwitch off any battery saver or background-data-limiting mode, and test the connection again before checking anything else, since it is a common and very quick cause to rule out.
2. 2Check the preferred network modeOpen the eSIM line's settings and confirm the network mode is set to 5G/LTE Auto or Automatic, not 3G Only or an older mode.
3. 3Open the network list and see what else is availableOpen the manual network selection page, temporarily switching off automatic mode to see the list of networks visible at that spot.
4. 4Try connecting to another listed network, one at a timeSelect another network and wait for the phone to finish registering, testing the connection before trying the next one if more than two options are listed.
5. 5Switch back to automatic before leaving the areaOnce satisfied with the chosen network, or before travelling on to another area, switch the selection back to Automatic so the phone does not lose signal entirely once it moves.

Common symptoms and their likely cause

Comparing settings people often confuse

eSIM plans and automatic partner-network steering

Many eSIM plans are built to connect through more than one partner network within the same country, to widen the chance you will have usable signal across different parts of that country. The phone hopping between these partners on its own is normal behaviour, not a fault, and does not mean anything is wrong with the profile.

The number and quality of partner networks vary by each plan's own supplier and destination country. We do not assert which network is faster in every part of that country, since that depends on the actual area and the time of use. For details on any specific plan, check that plan's own page or ask the team directly.

Device compatibility also plays a part here

Some phones do not support every frequency band used by each partner network, even though the phone supports eSIM and connects to data normally overall. The result can be that the phone only ever sees and can select some of the partner networks on the plan's list, not every network the plan supports in that country — which is not a fault in the profile but a limitation of the phone's own hardware.

If you suspect the phone itself may be the reason, check compatibility using the device checker before your next trip, to know in advance whether it supports the main frequency bands needed at the destination, rather than guessing at the cause once already at the destination with a slow connection.

Common mistakes

The most common mistake is selecting a network manually, then forgetting to switch back to automatic before moving areas, leading someone to mistakenly assume the plan itself has a problem when the phone was simply still clinging to a network with no signal in the new location.

Another common mistake is jumping to the conclusion that the connection is slow because of the wrong network, without first checking the battery-saving mode or the preferred network mode, even though both of those are quicker to fix and just as commonly the actual cause.

When switching networks still does not help

If every network on the list has been tried and none feels fast enough, consider that it may genuinely be a limitation of that area rather than a wrong setting. Some places see high user density at certain times of day, or the network infrastructure in that specific spot is simply limited. We do not hold data that can assert an exact speed for any given area, since it changes with time and location.

If you suspect the profile itself has a problem, rather than it simply being an area issue, contact the team via LINE or email with the country, the date, and the symptom described, so the system-side status can be checked directly.

What to check before concluding it is a network problem

• Turn off any battery-saving or background-data-limiting mode first
• Confirm the network mode is set to 5G/LTE Auto, not 3G Only
• Try manual network selection and compare it against automatic
• Switch back to Automatic before leaving that area every time
• Test again at a different time of day, since user density changes throughout the day
• Use the device checker to confirm the phone supports the necessary frequency bands

Check device compatibility