excuse me, pardon and sorry

We usually say excuse me before we interrupt or disturb somebody; we say sorry after we disturb or trouble somebody. Compare:
– Excuse me, could I get past? … Oh, sorry, did I step on your foot?
– Excuse me, could you tell me the way to the station?

– I beg your pardon is a more formal way of saying sorry.
– I beg your pardon I ‘m afraid I didn ‘t realize this was your seat.

If we do not hear or understand what people say, we usually say Sorry?
What?(informal) or (I beg your) pardon?
Americans also say Pardon me?
– ‘Mike’s on the phone. Sorry? I said, “Mike’s on the phone.”
– ‘See you tomorrow. ‘ ‘What? I said, “See you tomorrow.”‘
– ‘You’re going deaf.’ I beg your pardon?