You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Gregory Lee here.

ASSISTANT: How may I help you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, please wait a minute. There is no previous reservation found under your name.

USER: That's ok, may be something went wrong while I was doing my reservation. Thank you anyways.

ASSISTANT: Most welcome.