Q: If CS calls during deplaning (or sends a B2B message), I don’t have to call until the last pax is off the aircraft, correct?
It depends if this is at the end of the duty period after the last flight or if going into ground time.
If this is the end of the duty period, the B2B message would have to be sent prior to block in. If it wasn’t sent prior to block in, the Flight Attendant can ignore the message, and at the end of the duty period, the Flight Attendant has no obligation to return a call/voicemail from CS.
If this is deplaning prior to ground time (e.g. sit between flights), then yes, the Flight Attendant is required to call back after deplaning is complete.