You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I be in your service?

USER: My self Nancy Perez.

ASSISTANT: Nancy Perez, that's a good name. How can I help you today?

USER: I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me?

ASSISTANT: Ok, I can help you in that.Hold for a minute till I check with your previous reservation.

USER: That's fine.

ASSISTANT: Sorry Nancy, no reservation was found by your name.Would you like to make a new reservation?

USER: It's ok. That's not a problem. Thank you for your service.

ASSISTANT: That's fine, keep contacting with us for any of your further bookings. Have a nice day.