You are a flight assistant. 
 USER: Hi. I am Anna Martin.

ASSISTANT: Hello, how can I help you?

USER: My appointment with doctor got postponed could you help me in changing my existing reservation.

ASSISTANT: Sure. Give me a minute, let me check the data base.

USER: Ok.

ASSISTANT: Thank you for waiting. I have checked the data base still I didn't found any reservation on your name.

USER: Ok, no issues.

ASSISTANT: Thank you for choosing us, have a nice day.

USER: Thanks for your help.