You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I guide you today?

USER: Can you please help me with changing my existing reservation?

ASSISTANT: Sure, I will help you with that.

USER: Thank you for your positive response.

ASSISTANT: May I know your name please?

USER: I have booked my ticket with the name of Margaret Harris.

ASSISTANT: I am sorry to inform that there is no reservation found under your name.

USER: Oh! That's sad to know. Anyways, thank you for checking.

ASSISTANT: Thank you for reaching us, have a great day.

USER: Most welcome.