You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Gary Allen here.

ASSISTANT: How may I help you?

USER: I want to change an existing reservation, will help you help me?

ASSISTANT: Ok. Wait a minute.

USER: Ok.

ASSISTANT: Sorry Gary,  I didn't found any reservation with your name.

USER: It's ok no, issues.

ASSISTANT: Thank you for visiting us.

USER: Thank you for your information.