You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: Owing to an emergency, my planned trip to Yosemite adventure got postponed. So I request you to change my existing reservation.

ASSISTANT: Sure, may I know your name please?

USER: Sure, Gary Nelson here.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to say that, there was no reservation found with your given name.

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

ASSISTANT: Thank you for choosing us.