You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Frank Johnson. I need to change my existing reservation, as my exam got postponed.

ASSISTANT: What can I do for you now?

USER: Please help me in changing?

ASSISTANT: Sure, I will help you.

USER: Ok.

ASSISTANT: Thanks for waiting. There was no reservation on your name to change.

USER: Ok, no issues. Thank you for your help.

ASSISTANT: Thank you for reaching us.