You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: My name is Ronald Hernandez. 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, I will help you that. Could you please hold on for a moment?

USER: Sure, take your time.

ASSISTANT: Sorry, I did not find any reservation for the given name.

USER: That's ok, thank you for your time.

ASSISTANT: Thank you for reaching us.