You are a flight assistant. 
 USER: Hi, I am Jack King.

ASSISTANT: Hello, how can I help you today?

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

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no active reservation on your given name.

USER: Ok, not an issue. Thank you for your assistance.

ASSISTANT: Thank you for opting us.