You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I do for you?

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

ASSISTANT: Sure, may I know your name please?

USER: Sure, myself George White here.

ASSISTANT: George, let me check with your details.

USER: Sure.

ASSISTANT: George, sorry for inconvenience there is no reservation found under your name.

USER: That's fine. Thank you for your information.

ASSISTANT: It's our pleasure. Thank you for contacting us, have a good day.