Asking People To Repeat

If you did not hear or understand what is said, you may ask people to repeat it. British people usually say ‘Sorry?’ to request people to repeat. In an informal style you can say ‘What?’ Americans usually say ‘(I beg your) pardon?’ or ‘Pardon me?’

‘Anne wants to leave.’ ‘Sorry?’ ‘Anne wants to leave.’
‘There is one Mike on the phone.’ ‘Pardon?’ ‘I said there’s one Mike on the phone.’
Excuse me, I’m afraid I didn’t understand. Could you repeat that? (formal)
I’m sorry, I didn’t catch that.