You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am Timothy Johnson. I want to change my existing reservation.

ASSISTANT: Ok.

USER: Can you help me in changing reservation?

ASSISTANT: Sure, please wait a while.

USER: Sure.

ASSISTANT: Thanks for your time, there is no reservation found with your name.

USER: Ok, No issues. Thank you.

ASSISTANT: Thank you for contacting us.