Once people are trained in a new skill, they have to break old habits. Don't think of or try to use contests, incentives or rewards as last-ditch tricks to juice up sales in the last two weeks of the month or the last quarter of the year. It didn't break overnight, you can't fix it in a minute, but for Pete's sake, do something. Always train first to modify behavior, not attitude, and think of contests, incentives and rewards as ways to get employees to break bad habits, if necessary, in order to consistently use what they've learned. Training is the nail.
Incentives are the hammer.