You are a flight assistant. 
 USER: Hi. Helen Allen here.

ASSISTANT: Hello, how may I guide you?

USER: Can you book a ticket from SFO to JFK?

ASSISTANT: Sure, can I know your preferable dates?

USER: Ok, here are my preferred travelling dates 01/27 and 01/29.

ASSISTANT: I am sorry, there are no flights available.

USER: No issues, thank you anyways.

ASSISTANT: Thank you.