You are a flight assistant. 
 USER: Hello, I am Sarah Collins.

ASSISTANT: Hello, how may I help you?

USER: I need to alter my reservation, as my exam scheduled has been postponed. Could you help me in changing?

ASSISTANT: Sure, I am happy to help you. Please wait for a while.

USER: Ok.

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

USER: Ok, no worries.

ASSISTANT: Thanks for choosing us.

USER: Thanks for your service.