Calls fail abroad while data works: checking VoLTE roaming

What it looks like

• Outgoing calls fail or end after a second, while web pages still load.
• People say your phone went straight to voicemail although you had signal.
• Texts on your number arrive late or not at all.
• With Wi-Fi Calling on, calls work in the hotel and fail as soon as you step outside.

BEREC, the body of European telecom regulators, describes exactly this: when roaming, or wherever there is no 2G or 3G left to fall back on, a phone can have coverage and an internet connection and still not manage to make or receive voice calls. Where those older networks still exist, the phone quietly moves to them for the call and you never notice anything. Where they have been switched off, the call fails.

Four things that have to line up

• Your phone supports VoLTE and has it switched on for the line with your number.
• Your operator has VoLTE active on your account and SIM. Apple notes that some account types, such as business lines, and older SIM cards can block it.
• Your operator has a VoLTE roaming agreement with the network you are on. Australia's Telstra, for example, says its VoLTE calls abroad only work where it has such an agreement with the local partner.
• The phone and that network agree on the technical settings, which BEREC calls a specific problem in roaming where incompatibilities are likely.

Only the first point is in your hands from the settings. The other three explain why the same phone can call normally in one country and not in the next, or on one local network but not on another in the same city.

On an iPhone

Open Settings, then Mobile Data (Cellular in some regions). If you have two lines, tap your usual one, then Mobile Data Options, and look at Voice & Data. Apple's guide says that, depending on the model, operator and region, you may find a choice between Voice & Data, which is VoLTE, and Data Only. On iPhone 12 and later with a 5G plan, the Voice & Data menu is also where 5G Auto and LTE appear.

Data Only is the one to watch. Apple describes it as allowing mobile data but not voice calls over LTE, so calls have to use an older network; where there is none, they have nowhere to go. If the menu only lists network types such as LTE, 3G and 2G, Apple's older note on these options says that is what you see when the operator does not support VoLTE. And if a message says Cannot Activate LTE Calls, Apple's advice is to contact your operator, which may need to replace an older SIM.

On a Pixel or a Galaxy

On a Pixel, Google's steps are Settings, Network and internet, SIMs, and the VoLTE switch. Google notes that VoLTE may be on or off by default depending on the operator, and its guide to dropped calls lists checking VoLTE in that same menu. On a Samsung Galaxy, Samsung's help gives Settings, Connections, Mobile networks and the VoLTE calls switch; the wording can differ between models and operators.

Three details matter abroad. The preferred network type for that line has to include 4G, because VoLTE runs over it; Vodafone's device guides make that a condition for switching it on. On a dual SIM phone, check the line with your number, not the travel eSIM, which has no number and makes no normal calls. And Google suggests switching VoLTE off if you have unusual call or text problems: abroad, only try that where the local network still has 3G or 2G, or you may lose calls altogether.

Wi-Fi Calling takes another road

Wi-Fi Calling and VoLTE are easy to confuse, because both carry normal calls on your own number over an internet-based connection. The difference is the path. VoLTE runs over the foreign mobile network, so it depends on that network and on the roaming agreement. Wi-Fi Calling sends the call over Wi-Fi to your home operator through the internet, so the local mobile network plays no part; what matters is whether your operator allows it from abroad and how it bills those calls.

That makes it the natural fallback when VoLTE roaming fails: in the hotel or the flat, calls on your number can work again. The weak point is the edge of the Wi-Fi. Apple says that if Wi-Fi drops during a call, the call switches to the mobile network using VoLTE where available, so on a network without VoLTE roaming, a call that starts on Wi-Fi may end when you walk out of range.

What to try, and what to ask

• Turn airplane mode on and off, or restart, so the phone registers on the network again.
• Choose another local network by hand: roaming agreements are made network by network, so a different operator in the same country may carry your calls.
• Use Wi-Fi Calling wherever you have Wi-Fi, if your operator offers it abroad.
• For calls that do not need your number, use an app such as WhatsApp or FaceTime over mobile data.

Then ask your operator three precise questions: does it have VoLTE roaming with the network you are on in that country, is it active on your line, and does data roaming need to be on for it. The last one matters if you keep data roaming off on your usual line to avoid charges: one New Zealand operator, for instance, lists data roaming switched on as a requirement for VoLTE calls abroad and warns that it can bring daily roaming charges. Picking a network by hand is explained in manual or automatic network selection, and app calls over a data eSIM such as Snoozim's in calling home with a data-only eSIM.