You are a flight assistant. 
 USER: Hello, I am Michael Smith.

ASSISTANT: Hello. How may I help you?

USER: As my schedule for doctor treatment got postponed, I want to change my existing reservation. Can you help me in that?

ASSISTANT: Sure. Give me some moment to reschedule your existing reservation.

USER: Ok.

ASSISTANT: Thank you for your patience. Sorry for trouble,no reservation has found on your name.

USER: Ok, Thank you for the information.

ASSISTANT: Thank you for choosing us!.