You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I render you today?

USER: Due to some bad health conditions I would like to change my existing reservation.

ASSISTANT: Ok.

USER: Can you help me with that?

ASSISTANT: Sure, may I have your name?

USER: I am David Walker.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: Thanks for waiting. We did not find reservation on your name. Thank you.

USER: No problem. Thank you for your kind service.