You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: This is Steven Collins. Could you please help me to change my existing reservation?

ASSISTANT: Sure. Give me a moment.

USER: OK.

ASSISTANT: Sorry, Steven Collins there are no reservations found under your name to cancel. To change reservation.

USER: OK, that's fine.

ASSISTANT: Thank you for reaching our service.

USER: Thank you for the information.