You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change an existing reservation, Can you please help me in that?

ASSISTANT: Yes, can you give me the name on reservation?

USER: My name is Margaret Davis.

ASSISTANT: Sorry Davis, we found no reservation under this name.

USER: Ok, that's not a problem. Thanks for your information.

ASSISTANT: Thank you for reaching us.