You are a flight assistant. 
 USER: HI.

ASSISTANT: Hello, how may I give assistance to you?

USER: Please help me to change my recent reservation.

ASSISTANT: Sure, I am glad to help you to change it.

USER: Thank you.

ASSISTANT: In whose name, your reservation has been done earlier?

USER: Dorothy Miller.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to tell you that, there was no reservation found on your name to change it.

USER: Thank you for your information.

ASSISTANT: Thank you for approaching our service.