Sometimes, it is important to understand each piece of information when writing down a telephone number, or taking notes. Here are some phrases which you can use to ask people to repeat:
Would you mind repeating that?
Could I read that back to you?
Let me repeat that to double-check.
Person 1: The telephone number is 503 466-3978
Person 2: Let me repeat the number to double-check. 503 466-3978
Person 1: First, go down 3rd Ave to Black Street. Take a left, and continue on until you reach Harbor Blvd.
Person 2: Would you mind repeating that?
If you are at a party, or some other place where noise may interfere with your understanding, it's common to raise your voice a little and use one of the following phrases:
I'm sorry, I didn't catch (your name, the address, the name of the restaurant, etc).
Could you repeat that?
I'm having a problem understanding you. What's that again? (this phrase is also used on the telephone)
Person 1: Hi, my name is Peter. What's your name?
Person 2: Hi, I'm sorry, I didn't catch your name.
Person 1: It's a beautiful day today, isn't it?
Person 2: I'm having a problem understanding you. What's that again?