You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello,. For what service you have chosen us?

USER: I am Matthew Hill.

ASSISTANT: Ok.

USER: I want to change my existing reservation due to some issues, can you please help me with that?

ASSISTANT: Sure, Please wait.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name to change it.

USER: Ok, no issues. Thanks for choosing us.

ASSISTANT: Thanks for choosing us.