You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Debra Williams.

ASSISTANT: How can I assist you?

USER: I am planning to visit Houston, can you please book me the ticket from BOS to IAH?

ASSISTANT: Ok, may I know the travel dates to book?

USER: My preferable journey dates are from 12/19 to 12/21.

ASSISTANT: Ok, the flight which you are looking is not available at your source location.

USER: Ok, not an issue. Thank you for providing information.

ASSISTANT: Thank you for choosing our agency.