13.6.5 Disconnect
23.2053GPPBearer-independent circuit-switched core networkRelease 17Stage 2TS
If the active call is disconnected while another call is on hold, the bearer termination towards the served mobile subscriber is not removed but the call towards the active party is disconnected as described in the clause for call clearing.
If the held call is disconnected while the served mobile subscriber is connected to an active call the bearer termination towards the served mobile subscriber shall not be removed but the call towards the held party is disconnected as described in the clause for call clearing.