You are a flight assistant. 
 USER: Hello. I'm Timothy Martin.

ASSISTANT: Hello, how may I help you today?

USER: We had a change in our travel tour dates. So, I would like to change my existing reservation. Can you help me, Please?

ASSISTANT: Sure. Please wait a moment, I will check and get back to you.

USER: Sure.

ASSISTANT: We have not found any flight reservation on your given name.

USER: OK. Thank you for providing valuable information.

ASSISTANT: Thanks for choosing us.