You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: My convocation is going to held in Houston, can you book a ticket from IAD to IAH?

ASSISTANT: Sure, tell me your trip dates?

USER: My trip dates are 01/19 and 01/21. My name is David Perez.

ASSISTANT: Sorry, no flight available as per your details.

USER: No problem.

ASSISTANT: You are welcome.

USER: Thank you for searching.

ASSISTANT: Have a nice day.