You are a flight assistant. 
 USER: Hello, I am Steven Walker.

ASSISTANT: Hello, how can I assist you?

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

ASSISTANT: Sure, we are here to help you. Please wait a moment.

USER: Ok.

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

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you for choosing us.