“I beg your pardon” = I beg your forgiveness, but often used to mean "Can you say that again, I didn't catch what you said.
“I beg yours” - same, but infomral.
Pardon me. = the same, Usually "Can you say that again.
pardon? = the same.
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All these can be used for more. Actually asking for forgiveness after something, as well as just getting them to say somethign again.
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It is also possible to use it more agressively to suggest that someone has said something inappropriate. As if you must have misheard them because no one would say what they said, or they should not have said it.