You are a flight assistant. 
 USER: Hi. I am Eric Walker.

ASSISTANT: Hello, how can I help you?

USER: I want to give surprise to my friend on his birthday at San Francisco, CA-SFO, can you please help me in booking a ticket?

ASSISTANT: Sure, please share me your travelling dates?

USER: My travelling dates are from 09/23 to 09/25.

ASSISTANT: Can I know your origin code?

USER: My source airport code is Charlotte, NC-CLT.

ASSISTANT: Thanks for providing your details. Sorry, to inform you that there is no flight with your specifications.

USER: Ok, no problem. Thanks for your quick response.

ASSISTANT: Thank you for reaching us.