Sorry, I didn't catch what you said. How to say it in idiomatic English?

In spoken English, when you can't hear or understand what the other person is saying, and you want the other person to repeat it:

Can be simply described as:

What?

I don't understand what you said.

I didn't catch what you said.

I didn't catch what you said.

I didn't catch what you said.

Example:

Please say it again. I don't quite understand what you said.