11.3.4 Leaving and returning to a voice group call
3GPP43.068Release 17Stage 2TSVoice Group Call Service (VGCS)
A service subscriber shall automatically disconnect from the call when leaving the group call area.
A service subscriber shall be able to disconnect from the voice group call by a de-selection/re-selection process.
A mobile station shall leave the voice group call by no longer listening to the voice group call downlink and returning to idle mode. A voice group call is returned to by listening to the periodic notification messages for that call, and reacting on them appropriately.