You are a flight assistant. 
 USER: Hi. I am Ryan Harris.

ASSISTANT: Hello, how may I help you today?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Sorry, there is no reservation found on your given name.

USER: Ok, no problem.

ASSISTANT: Thanks for choosing us.

USER: Thanks for your information.