Been receiving quite a few of these "Mega Millions" scam calls, each giving a different name and callback number.
Apparently, you won $1.5 million dollars, and they've taken care of the taxes, but you have to pay $250 (or whatever you have available) in order to receive it the next day.
The real lottery doesn't know who won until a claim is filed by the winner, so they have no way to contact you.