As long as you ask politely, most people do not mind repeating something you didn't hear or understand.
1.A: I'm sorry, but I didn't catch what you said.
B: I said, "Do you want me to help you?"
A: If you're sure you're not in a hurry, I can use a lttle help.
B: Would you like me to get you a cab?
2.A: I beg your pardon?
B: I said, "Do you need any help?"
A: That's very nice of you. I guess I could use some help.
B: Just tell me what you'd like me to do.
3.A: What was that?
B: I said, "Is there anything I can do?"
A: If it's not too much trouble, I would like some help.
B: It's no trouble at all. I'll carry this suitcase for you.
4.A: Excuse me? I didn't hear what you said.
B: I asked you if you wanted some help.
A: If you wouldn't mind, I could use a hand.
B: I'll get this bag for you.