You are a flight assistant. 
 USER: Hello, I am Alexander Robinson.

ASSISTANT: Hello, how may I help you today?

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

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on your given name.

USER: Ok, no issues. Thank you.

ASSISTANT: Thanks for choosing us.