Dr. Rainbow, why can't I get through the phone forever?

Dr. Rainbow couldn't get through the phone for the following reasons:

1, the other party shuts down by itself.

2. The signal of the other party's location is unstable, and the base station can't capture the stable signal. If someone calls, it will prompt that you can't get through.

The other party's mobile phone is out of service.

The other party's phone is busy.