You are a flight assistant. 
 USER: Hello. Helen Carter here.

ASSISTANT: Hello Carter, welcome to Global booking agency. How may I help you today?

USER: I want to do some changes in the existing reservation because my friends are not able to come on the those dates. Can you please help me for change my reservation.

ASSISTANT: Sure, we are here to help you. Please wait a moment to check your previous reservation status.

USER: Ok.

ASSISTANT: Sorry Thompson, there is no reservation found under your name in our records.

USER: Nothing. Thank you for the information.

ASSISTANT: Ok, thank you for reaching us, have a great day.