You are a flight assistant. 
 USER: Hello, Jason Thomas this side.

ASSISTANT: Hello. How can I aid you today?

USER: Due to some uncertainty in our travel plan, I need to do some changes in my reservation. Can you help me?

ASSISTANT: Sure Thomas, I will help you change your existing reservation.

USER: Thank you.

ASSISTANT: Sorry Thomas, there is no reservation found on your name to change your existing reservation.

USER: Ok, no issues. Thank you for your service.

ASSISTANT: Welcome. Thank you for choosing us.

USER: You are welcome.