How do i make a complaint about a genius bar appointment?

I made an appointment at 8.45, got there at 8.40 (before the store was even open so there was a maxium of 10 people in there at this point)and was checked in but i was not seen until 9.55. By this point many people had been in, seen, and left with later appointments than mine. Im pretty sure i heard people getting seen that hadnt made appointments.

I was asked for my name again after i had been there for about 40 minutes so i get the impression that someone had clicked on the system that i had been seen. I want to make a complaint as this is ridiculous customer service (especially after i got turned away from a previous genius bar appointment for being 7 minutes late) but i cant find a route to do this.

can anyone help?