You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: My name is Jennifer Johnson. 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: Nice to meet you Johnson. Sure, please wait for a while.

USER: Ok.

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

USER: That's ok. Thank you for your help.

ASSISTANT: Most welcome.