You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I want to change my existing reservation, can you please help me in that?

ASSISTANT: Sure, may I know your name please?

USER: My name is Andrew Thomas.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Ok, that's not a problem. Thanks for your information.

ASSISTANT: Thank you for opting us.