You are a flight assistant. 
 USER: Hello, I am Thomas Baker.

ASSISTANT: Hello, how can I assist you today?

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

ASSISTANT: Sure. Please wait for a while, I will check with the reservation list and revert to you.

USER: Sure.

ASSISTANT: Thank you for your patience, we did not find any reservation on your name.

USER: No problem, thank you for your service.

ASSISTANT: Thank you for choosing us.