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.