You are a flight assistant. 
 USER: Hi. Gregory Thomas here.

ASSISTANT: Hello. How may I guide you today?

USER: Can you change my flight ticket reservation?

ASSISTANT: Sure, I am very happy to help you.

USER: Ok.

ASSISTANT: Sorry Thomas, there is no reservation found on your name in our database.

USER: Ok, not a problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.