You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I be at your service today?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: Sure, my name is David Allen.

ASSISTANT: Ok, please be on hold.

USER: Ok, I will wait.

ASSISTANT: Sorry we did not find any reservation on your name in our database.

USER: Ok, no problem. Anyways, thank you for your service.

ASSISTANT: Thank you for choosing us.