No phone line necessary.
Um, you watch the rotating Whopper for 5 minutes. They randomly make you hit a key on the remote to make sure you're paying attention. If you do the 5 minutes they send you a coupon for a free Whopper. You can then do a 10 minute one and a 15 minute one, each for another free Whopper (30 minutes total = 3 free Whoppers). Honestly it isn't any worse than staring at some of the other craptastic half hours that are on..