You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,.

USER: I am David Moore.

ASSISTANT: How may I help you?

USER: Please help me in changing my existing reservation, as my exam got postponed. Please help me in changing?

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: No reservation found.

USER: Ok, no issues.

ASSISTANT: Thanks.