Your call drops part-way through

Drops that cluster around a consistent duration are being caused by something counting. The most frequent culprit is a router's connection-tracking timeout: the router keeps a record of each open connection and discards records it considers idle, and because voice packets are small and steady rather than bursty, some routers misjudge an active call as idle. The tell is that the call dies quietly, with no error and no warning, always at about the same point.

Power management is the other timed cause and it is the one to suspect on Android. Every major manufacturer runs its own battery optimisation on top of the operating system's, and the more aggressive implementations suspend an app shortly after the screen turns off regardless of what the app is doing. A call that survives while you look at the screen and dies about thirty seconds after you put the phone to your ear and the display sleeps is this, almost every time.

Random drops, by contrast, are the network. Every WiFi network loses packets; the question is how many and in what pattern. A short burst of loss produces a gap in the audio and the call recovers. A longer one — a handover between access points, a microwave oven, a neighbour's network on the same channel — exceeds what the call can ride out and it ends. Mobile networks do the same thing during a handover between cells, which is why calls made while moving through a city drop more than calls made sitting still.

It is worth ruling out the explanations people reach for first, because time spent on them is time not spent on the cause.

Your balance is not cutting the call. Telvio bills per second from prepaid credit, and a call that would exhaust the balance ends with the balance at zero — which means the drop happens at a predictable cost, not a predictable time, and the app shows the remaining time before you dial. If you suspect billing, what a call actually costs shows the arithmetic.

There is no call-length limit. Some services cap a call at an hour or cut a free trial call at a fixed point; Telvio does not, so a two-minute drop is not a policy.

The person you called is very rarely the cause. If they are on a mobile in a weak signal area their end can certainly fail, but the giveaway is that it happens with everyone you call rather than with one person. Drops confined to one recipient point at their network, not yours.

Office, campus and hotel networks are often configured by people whose priority is not your call, and there is a limit to what you can do from the handset. Two things are worth trying before giving up on the network.

Mobile data almost always works where restrictive WiFi does not, because the mobile network carries the traffic to its own core before it reaches the internet and there is no local firewall in the path. A minute of voice costs very little data — the figures are on the connection page — so this is a cheaper answer than it sounds.

Where WiFi is your only option and it filters voice, ask whoever runs it whether VoIP is permitted. On a corporate network the answer is often that it is allowed but needs a rule; on a hotel network there is sometimes a premium tier that does not filter. Neither is satisfying, but both are faster than reconfiguring a phone that is working correctly.