ASKING FOR REPETITION
I'm afraid I didn't understand that. Could you repeat what you just said?
I didn't catch that. Could you repeat that, please?
I missed that. Could you say it again, please?
Could you run that by me one more time?

Asking for Clarification

I don't quite follow you. What exactly do you mean?
I'm afraid I don't quite understand what your are getting at.
Could you explain to me how that is going to work?
I don't see what you mean. Could we have some more details, please?

Asking for Verification

You did say next week, didn't you? ('did' is stressed)
Do you mean that...?
Is it true that...?