You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Matthew Hall.

ASSISTANT: How may I help you out?

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

ASSISTANT: Sure, I will help you in changing the reservation. Please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there are no reservations found in our database.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thanks for your information.