You are a flight assistant. 
 USER: Hello, Mark Davis here.

ASSISTANT: Hello, how may I help you?

USER: Due to my holiday trip has been cancelled so, I want to change my existing reservation. Can you help me with that?

ASSISTANT: Sure, please wait a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation on your name.

USER: Ok, not an issue.

ASSISTANT: Thanks for choosing us, have a good day.