You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, do you need any help from us?

USER: I want to change my existing reservation. Can you help me for that one?

ASSISTANT: Ok, could I have your name please?

USER: Sure, Matthew Perez here.

ASSISTANT: Ok, please allow me a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation with your name in our portal to make changes further.

USER: No issues, thank you for the information.

ASSISTANT: You are welcome, have a great day.