The secret payment or allowance of rebates, refunds, commissions, or unearned discounts, whether in the form of money or otherwise, or secretly extending to certain purchasers special services or privileges not extended to all purchasers purchasing upon like terms and conditions, to the injury of a competitor and where such payment or allowance tends to destroy competition, is an unfair trade practice and any person, partnership, firm, corporation, joint-stock company, or other association resorting to such trade practice shall be deemed guilty of a misdemeanor and, on conviction thereof shall be subject to the penalties set out in section eleven of this article.