You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: I am Virginia Thomas. I am planning to go for hop-on hop-off tour at Houston, IAH. Can you please book a ticket on 12/18?

ASSISTANT: Sure, may I know your another journey date with airport code?

USER: I will return on 12/20. Source code is Boston, BOS.

ASSISTANT: Give me a minute.

USER: Sure.

ASSISTANT: Sorry, there is no flight found on your given dates.

USER: No problem. Thank you.

ASSISTANT: Thank you for opting us.