You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I'm Pamela Lopez, I want to go for a trip to San Francisco. Can you please book me the ticket?

ASSISTANT: Sure, please tell your travelling airport codes.

USER: My source and destination airport codes are LAS and SFO.

ASSISTANT: When would you like to travel?

USER: I'm planning to take off on 02/20 and return on 02/22.

ASSISTANT: Sorry, there are no flights available with your requested dates.

USER: That's ok, I will try to go by train. Thank you anyways.

ASSISTANT: Thank you and have a nice day.