You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Sharon Thomas.

ASSISTANT: How can I assist you?

USER: Due to emergency I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Ok. Wait a minute. Thanks for waiting, There is no reservation found with your name.

USER: Sure. Ok, no problem. Thanks for your information.

ASSISTANT: Thanks for choosing us.