A new report from GoBankingRates.com reveals that some gas stations and convenience stores, among other merchants, are illegally imposing fees on customers who pay with a debit card. "Checkout fees" for buyers who use credit cards were sanctioned as part of January's settlement of a class-action lawsuit, but the agreement did not cover debit cards. Even so, some retailers are still applying the fee to debit cards; and others are simply offering discounts for cash buyers, which does not add a charge for users of plastic but penalizes them just the same. In addition to the questionable fees, some of these merchants are requiring minimum purchases for customers who use bank cards -- even though Visa and MasterCard have confirmed that this practice is not allowed. Consumers who encounter these problems should call the customer service number on the back of their cards and report them.