Dear Liang Xiaomin,
Thanks for this much information!
I want to ask one thing-
Sorry to say but according to my experience in this field, customer feel irritated if we put questionnaire in front of them on call. Customer always want a very short conversation with Customer Care. Your idea to put the survey questions in the mail was fine but on the call, I think it will not work.
Rest of the decision is depends on you and I will respect your final decision.