answer: #Person1# helps #Person2# to change #Person2#'s phone number.
documents: #Person1#: Hello. This is the Customer service. How can I help you?
  #Person2#: Yes. I'Ve been getting harassing calls recently. Can I have my phone number changed?
  #Person1#: Sure. What's your favorite number?
  #Person2#: How about 560 436 4040.
  #Person1#: I'm sorry. This number has already been registered.
  #Person2#: How about 560-436-8976?
  #Person1#: This number is ok. It's still available. When would you like your phone number changed?
  #Person2#: As soon as possible. Can I have it right now?
  #Person1#: Sure.
  #Person2#: Thanks.