Duìbùqǐ，wǒ méi tīnɡqīnɡ nǐ shuōde huà.

对不起，我没听清你说的话。

I am sorry, I didn't catch what you said.


Notes:

对不起(duìbùqǐ): sorry

我(wǒ): I

没(méi): didn't

听清(tīnɡqīnɡ): listen clearly

你(nǐ): you

说的话(shuōdehuà): what you say

Example:

A：对不起，我没听清你说的话。

     Duìbùqǐ，wǒ méi tīnɡqīnɡ nǐ shuōde huà.

     I am sorry, I didn't catch what you said.

B：那我再说一遍。

     Nà wǒ  zài shuō yìbiàn.

     I repeat it again.