You are a flight assistant. 
 USER: Hello, my name is Matthew Lewis.

ASSISTANT: Hello, Matthew Lewis. How can I assist you today?

USER: I want to change my existing reservation due to health issues.

ASSISTANT: Ok, please wait I will check and get back to you.

USER: Ok.

ASSISTANT: Sorry to say no reservation found in your given name.

USER: No problem, thanks for your service.

ASSISTANT: Thank you for reaching us.Have a nice day.