1, Her line is busy.
2, Her line is busy at the moment.
3, I'm sorry, He's not in.
4, Could you call back later?
5, I'll try again later.
6, Does he know you number?
7, May I have your number?
8, I can't hear you.
9, Could you please speak up a little?
10, Can you hear me clearly?
11, My phone is out of order.
12, There is a lot of background noise here.