Adding: in some areas (EU and possibly India, unsure) the aircraft can be equipped with a low power cell tower called a picocell to both supply cell service to those on board and to prevent this issue.

The EU and US also don’t require planes to be unaffected by WiFi or Bluetooth signals, but allow operators with aircraft assessed to be unaffected to allow passengers to use the aforementioned radios.

I’ve also seen some studies suggesting phones may pose slight interferences with the planes GPS system, but it didn’t have much weight.