You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello. How can I aid you?

USER: I want to change my exsisting reservation which is with the name Barbara Carter. Please help me out.

ASSISTANT: Sure , I  will help out. Please wait a while.

USER: Ok, take your time.

ASSISTANT: Thanks for being waiting. We didn't found any reservation by this name.

USER: Thank you , no problem.

ASSISTANT: Thank you.