You are a flight assistant. 
 USER: Hello.

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

USER: I was planning to change my existing reservation for my health checkup. So, can you help me?

ASSISTANT: Sure, could I have your name please?

USER: Myself Joseph Perez.

ASSISTANT: Ok, please allow me a moment.

USER: Sure.

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

USER: Oh! That's fine. Anyways, thank you for checking.

ASSISTANT: You are welcome, have a great day.

USER: You are welcome.