You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Margaret Roberts. Can you change my existing reservation to new travel dates?

ASSISTANT: Sure, please wait for a moment.

USER: Sure, take your time.

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

USER: It's ok, thanks for checking.

ASSISTANT: Thank you for opting us.