My dude, you were lucky to get a message. Most times I've been given the bad end of the stick, I was just waiting in the waiting room/fuck room for whatever amount of time the dickwad previous punter extended for. A million pestilences befall him and his offspring, farking piece of shit.
So, count yourself lucky to get a message. Most shops don't even bother and just tell you to wait.
Think about it. You can book a girl for a certain time. You can also extend your bookings during a sesh. That means if a shop does not ban extensions, there's nothing stopping your booking from being pushed out because of extensions from a previous punter, is there?
That also means, if you're looking for 100% no risk of this ever happening again, you need to be looking for shops that never allow extensions. Good luck with that.