You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Betty Thompson.

ASSISTANT: What services that I can help you at this moment?

USER: I am planning to change an existing reservation, due to some urgent work.Can you help me out to change my reservation?

ASSISTANT: Sure, I am happy to help you.

USER: That's great.

ASSISTANT: Please wait to check your reservation to do the changes.

USER: Ok, take your own time.

ASSISTANT: Betty, I am sorry to say that, there is no reservation found on your name to modify it.

USER: That's really sad. Thank you for your service.

ASSISTANT: You are welcome and thank you for your time in approaching us.