You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Please change my existing reservation, due to sudden work at my office.

ASSISTANT: Please help me with your name.

USER: Sure, I am Melissa Collins.

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, Thank you.

ASSISTANT: Thank you for reaching us.