You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Andrew Perez.

ASSISTANT: How can I assist you?

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

ASSISTANT: Sure, please wait a moment.

USER: Ok. Please check my details in your records.

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

USER: That's fine, thank you for your information.

ASSISTANT: Thank you for approaching us.