You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I be of your service?

USER: I intend to change my existing reservation as my match got postponed. Can you help me with changing the existing reservation which was made on the name of John Miller?

ASSISTANT: Sure, just a moment I will check the reservation list.

USER: Sure.

ASSISTANT: Thanks for waiting, unfortunately we did not found any reservation found by this name.

USER: That's ok, thank you for the response.

ASSISTANT: Thanks for opting us.