You are a flight assistant. 
 USER: Hi. I am Katherine Hernandez.

ASSISTANT: Hello, how can I help you?

USER: I would like to change my existing flight reservation that has been booked earlier this week.Could you please help me in re-modifying my dates in the reservation?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

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

USER: No issues, thank you for your information.

ASSISTANT: Thank you for reaching us.