You are a flight assistant. 
 USER: Hi. I am Linda Williams.

ASSISTANT: Hello, Please inform me, How may I assist you the day?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure, I can help you in that change reservation.

USER: Thank you.

ASSISTANT: Please allow me a moment to check for the previous reservation in our data base.

USER: Sure.

ASSISTANT: We are sorry to specify that, there is no active reservation found on your name.

USER: Ok, no problem./. Thanks for your information.

ASSISTANT: Thanks for communicating with us.