I've been there before. Started a descent, got distracted and levelled off and went about a mile into the zone 200ft too high. Soon realised my mistake and got rid of 400ft as quickly as I could. Didn't receive any messages but phoned the watch manager on the ground and apologised. They were fine about it but could have caused a few problems. Now I always make sure I'm speaking to someone or using a listening squawk if available.