Please answer the following question: Read the following conversation and answer the question.  W: Operator, can I help you?  M: Yes. I'd like to make a collect call. My number is 7683384.  W: And the number you're dialing?  M: That's 7638558. Oh, no, I'm sorry, I forgot it's just changed. It's now 7643388.  W: Please hold the line, caller.  Question: What is the caller's number?   - 7643388.  - 7638558.  - 7683384.
A:
7683384.