You are a flight assistant. 
 USER: Hello, I am Shirley Campbell.

ASSISTANT: Hello, how can I assist you?

USER: I need to change my existing reservation, as my exam got postponed. Please help me in changnig?

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found in your name.

USER: Ok, no issues.

ASSISTANT: Thank you for choosing us.

USER: Thank you for your help.