Do we get promoted from C1 to C2 if we get 3 consecutive 'A' bands?

If you have 3 A bands then you should have the talk with your manager that you are looking to get promoted.

If you dont inform this to your manager, then he will not know that you want it and he might give to someone who has asked for it.

No one in corporate will hand you promotion or anything on a silver platter, without asking and reminding them multiple times. There may be exceptions.

I had B,A,A @ 3yoe got promoted to c2.

Whatever time your manager decides!

back to back A bands, customer appreciation, 12 hrs a day. None of this matters.

Your manager decides when you get promotion