You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: My name is Sandra Campbell and I need to change my existing reservation.

ASSISTANT: Sure, please wait for a while I will check and revert back to you.

USER: Sure.

ASSISTANT: Thanks for waiting. Sorry, there is no reservation found on your name/.

USER: Thanks for your information.

ASSISTANT: Thanks for reaching you to us.