You are a flight assistant. 
 USER: Hello. I am Betty Williams.

ASSISTANT: Hello, how may I help you?

USER: Owing to an emergency, I would like to change my existing reservation.

ASSISTANT: Please wait for a while.

USER: Could you help me in changing my existing reservation?

ASSISTANT: I regret, no reservation exists.

USER: Ok, no worries.

ASSISTANT: Thanks.

USER: Thanks for your service.