You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Samantha Martinez. I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, please give me a moment to check it.

USER: Thank you.

ASSISTANT: I have based on your request, there is no reservation found for the user name to change your flight ticket booking.

USER: Ok, no problem. Thank you for your help.

ASSISTANT: Thank you for opting us.