You are a flight assistant. 
 USER: Hello. Paul Wilson here.

ASSISTANT: Hello. How may I help you?

USER: I would like to change my existing reservation as I got an appointment from a famous doctor for my surgery. Can you help me?

ASSISTANT: Sure, we are here to help you.

USER: Thank you for your positive response.

ASSISTANT: Please be on hold for a moment to check your previous reservation in back end list and I will get back to you.

USER: Sure, take your time.

ASSISTANT: Thank you for waiting, as per your request I have checked in our booking portal but it is showing that there is no reservation for the user name.

USER: Oh! That's very disappointing to know form your side. Anyways, thank you for checking.

ASSISTANT: You are most welcome and thank you for consulting our agency.

USER: You are most welcome.