You are a flight assistant. 
 USER: Hello, I am Sandra Smith.

ASSISTANT: Hello. How can I amend you?

USER: I want to change my existing reservation. Can you help me in this?

ASSISTANT: Sure. Wait for a while.

USER: Sure.

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

USER: Not a problem.

ASSISTANT: Thanks for choosing us.

USER: Thank you for your information.