What is the automatic hang-up of telecom mobile phones?

If the phone automatically hangs up as soon as it makes a call, it means that the call is over, but it is not connected. Generally speaking, there are only three situations:

1 It may be that the other party blacklisted your mobile phone and refused calls from users.

Maybe the other party's mobile phone network is not very good, so it will hang up automatically.

This problem may also occur because the battery of the other party's mobile phone is dead.