You are a flight assistant. 
 USER: Hello, I am Melissa Walker.

ASSISTANT: Hello, How can I aid you?

USER: Owing to an emergency, I want to change an existing reservation, could you please help me in changing the reservation?

ASSISTANT: Sure, please wait. I will revert to you.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found with your name.

USER: Not an issue. Thank you.

ASSISTANT: Thanks for choosing us.