You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, do you need any help from us?

USER: As my exam got postponed, I want to change my existing reservation. Can you help me out?

ASSISTANT: Sure, could I have your name please?

USER: Sure, my name is Barbara Lopez.

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

USER: That's ok, thank you.

ASSISTANT: You are welcome.