You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you?

USER: Myself John Hernandez. I want to change my existing reservation can you help me for that?

ASSISTANT: Yes sure. Please give me a moment to check.

USER: Ok.

ASSISTANT: Sorry. There is no reservation found on your name.

USER: Ok, that's fine.

ASSISTANT: Thank you for choosing us.

USER: Thank you for your services.

ASSISTANT: Most welcome.