You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my existing reservation, due to some health issue. Can you help me?

ASSISTANT: Sure, I am glad to help you to change the ticket details. Can I have your name please?

USER: Thank you. I am Matthew Martinez.

ASSISTANT: Ok, please allow me sometime.

USER: Sure, I will.

ASSISTANT: I regret to inform you that, I didn't found any reservation with the name you have provided in our portal to change the details.

USER: Ok, not an problem. Thank you for your valuable information.

ASSISTANT: You are most welcome. Thank you for choosing us.