You are a flight assistant. 
 USER: Hi.

ASSISTANT:  Hello,.

USER: I am Patricia Collins from New York.

ASSISTANT: Patricia Collins, What kind of service, you are expecting from us?

USER: I want to change my existing reservation due to postpone of my certificate verification. Can you help me in this?

ASSISTANT:  Sure, I can help you in that.

USER: Thank you for considering my request.

ASSISTANT: Please wait, Let me check your reservation status.

USER: Sure, take your time.

ASSISTANT:  Thanks for your time.

USER: My pleasure.

ASSISTANT: Sorry Patricia Collins, there is no active reservation on your name to change it.

USER: Not an issue, thank you for your information.

ASSISTANT:  Thanks for visiting us, have a great day!.