You are a flight assistant. 
 USER: Hello. I am Williams Thompson.

ASSISTANT: Hello, what sort of help are you seeking from us?

USER: I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Sure, we are here to help you in that.

USER: Thank you.

ASSISTANT: There is a reservation found on your name, to proceed further I need to know your new journey dates?

USER: I am planning to travel on June 23 and return back on June 25.

ASSISTANT: Ok, may I know your boarding and landing airport codes?

USER: My source code is DEN and my destination code is LGA.

ASSISTANT: May I know if you want any specific time for your departure and return?

USER: Yes, my depart time should be afternoon.

ASSISTANT: Do you like to go with a economy class or business class?

USER: I am ok with any class.

ASSISTANT: Do you prefer any lay by in between journey?

USER: Yes, I am looking for a connecting flight.

ASSISTANT: Thanks for your details, there are no flights available at this moment matching your particulars.

USER: That's fine, thank you for your service.

ASSISTANT: Thanks for communicating with us.