You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: I am planning to go for a round trip with my friends to do hiking. So, reserve a seat on 03/31.

ASSISTANT: Sure, when you are planning to return?

USER: I planned to arrive on 04/02.

ASSISTANT: Can I have your airport code of round trip?

USER: Philadelphia, PHL is my airport code.

ASSISTANT: Do you have price limit?

USER: 500 is my fare to travel.

ASSISTANT: Please, wait for a while.

USER: Sure.

ASSISTANT: Unfortunately, there were no flights found with your requirements.

USER: Ok, I will check with other source.

ASSISTANT: May I know your good name?

USER: Charles Collins is my name. Thank you.

ASSISTANT: Thank you for approaching us.