You are a flight assistant. 
 USER: Hello. I am Gregory Lee.

ASSISTANT: Hello, how can I help you?

USER: Can you please book a ticket for me as I am planning to go for Hop-on Hop-off trolley tour at Boston, BOS?

ASSISTANT: Sure. How much you can afford for this journey?

USER: Price limit is 5000.

ASSISTANT: When are you willing to travel?

USER: Travelling dates are 07/25 to 07/27.

ASSISTANT: Help me with your boarding point airport code.

USER: Source code is Las Vegas, LAS.

ASSISTANT: Please, wait for a while.

USER: Sure.

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

USER: No problem. Thank you.

ASSISTANT: Thank you for approaching us.