We may say it's just a little small thing, not worth taking it seriously or complaining.

But I can tell you a decent shop would make sure you get the time you pay for, or you pay for the time you get. Simple and period.

In this case, this shop FAILED to manage the booking in the first place, FAILED to inform customer the change of appointment time, FAILED to charge the right fee. The worst thing was, these were all done deliberately, to the shop's favor, to take advantage over a customer who did nothing wrong.

To OP: I would suggest you go other places, or at least have a chat to the shop if you still see value going back.