You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am William Campbell, have to change existing reservation. Can You help me in that issue?

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

USER: Sure.

ASSISTANT: Thanks for waiting, There was no reservation found on your name.

USER: Ok, thanks for sharing information.

ASSISTANT: Thanks for contacting us.