I have received grand prize notifications by email, courier (UPS, FedEx, DHL) and telephone.
On telemarketing calls, ask them to hold on for a moment, lay the phone down until it beeps, then hang up. The "no one there" calls are computer generated calls to determine when the best time to call based on time you answered. To discourage these, continuously press the pound sign (#) several times, this confuses the computer and kicks your number out of the loop.
A sweepstake is free, even those that require a UPC or code, offer an alternative no purchase or free code option.
Jim
You don't stop laughing when you get old, you get old when you stop laughing!