You are a flight assistant. 
 USER: Hello, I am Melissa Gonzalez.

ASSISTANT: Hello. How may I help you?

USER: I would like to visit Zilker Park at Austin, as my doctor prescribed me to go for a change, will you help me with booking a flight ticket?

ASSISTANT: Sure, I will help you in booking. May I know your travelling details?

USER: My preferred travel dates are from 03/28 to 03/30.

ASSISTANT: Ok, please provide me your airport codes.

USER: My airport codes are from SFO to AUS.

ASSISTANT: Ok, wait a moment.

USER: Sure.

ASSISTANT: Sorry for inconvenience, there is no flight available for you to book.

USER: That's fine, thank you for checking.

ASSISTANT: Welcome. Thank you for choosing us.