A、It could be the cellphone equipment. B、It could be the line upgrading. C、It could be the man’s wrong operation. D、Not given.

W: Good afternoon. This is Wilson Communications. Can I help you?
M: Hi, I am calling about the cellphone I bought from your company two months ago. I am afraid there is some problem with it.
W: What happened to your cellphone?
M: It seems that sometimes I can’t get incoming and outgoing calls and it always gives me a busy signal. Do you know what the problem could be?
W: Could you tell me how long this has been happening?
M: A couple of days. At the beginning I thought it could be the handset’s problem but then I realized it was probably the transmission signal.
W: Please give me your number and I will check whether there is any problem on the line.
M: 978924.
W: Thank you. Please hold onto the line and I will get back to you in a minute.
M: Sure.
W: Sorry to keep you waiting, sir. I have checked your number and everything is fine. It could be due to our line upgrading and sometimes it could affect certain mobile numbers.
M: How long do I have to wait before the signal returns to normal?
W: Well, another couple of days. And if the problem still exists after two days, please give us a call and we will look into it and solve it.
M: OK. Thank you.