You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I abet you?

USER: Gregory Roberts this side. I want to change my existing reservation, due to some health issue. can you please help me?

ASSISTANT: Sure, I will help you with that. Can you please wait while I check?

USER: Ok, take your time.

ASSISTANT: Sorry Gregory, there is no reservation on your name.

USER: It's ok, thank you for checking.

ASSISTANT: Thank you for reaching us.