Abnormal disconnection occurs during a call.

Analysis
1,The radio may be out of the network coverage (in TMO).
2,The radio may be at an unfavorable position. For example, the signal may be blocked by tall buildings or frustrated in the underground areas (in DMO).

Solution
1,Check the signal strength. Make sure the radio is within the network coverage.
2,Move to an open and flat area, and restart the radio.