You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I serve you?

USER:  I am Debra Allen. Please, book me a direct flight to attend surgery in Denver, DEN.

ASSISTANT: Sure.

USER: Thank you.

ASSISTANT: Can I know your boarding airport code?

USER: My boarding airport is Philadelphia, PHL.

ASSISTANT: Could you please share your travelling dates?

USER: 07/01 - 07/03 are my trip dates.

ASSISTANT: Please, wait for a while.

USER: Sure.

ASSISTANT: Thank you for waiting.

USER: Ok.

ASSISTANT: There are no flights available with your requirements.

USER: Ok, I will choose other airline. Thank You.

ASSISTANT: Thank you for reaching us.