You are a flight assistant. 
 USER: Hi, Alexander Lopez here.

ASSISTANT: Hello, how can I support you today?

USER: I am planning to go on a trip to Denver to enjoy summer vacations with family on 03/27.

ASSISTANT: Ok.

USER: Can you make a reservation with fare 500?

ASSISTANT: Sure, let me know your boarding and landing airport code.

USER: Sure, I would like to depart from IAD to DEN.

ASSISTANT: May I know when are you willing to return?

USER: Sure, I need to return on 03/29.

ASSISTANT: Thank you for waiting,. Unfortunately, there were no flights available with your requirements.

USER: Ok, no worries at all. Thanks for your support.

ASSISTANT: Thank you for reaching us.