You are a flight assistant. 
 USER: Hello,. I am Jack Moore.

ASSISTANT: Hello, how could I serve you today?

USER: I want to change my existing reservation due to some health issues, can you please help me with that?

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: Sorry to inform, there is no reservation found with your given name.

USER: Ok, no issues.

ASSISTANT: Thank you for choosing us.

USER: Thanks for your service.