Visa Inc. and MasterCard Inc., the world's largest payments networks, are once again facing criticism from U.S. Senator Richard Durbin over bank-card fees. Durbin, the Illinois Democrat whose amendment to the 2010 Dodd-Frank Act capped debit-card swipe fees, sent a letter Thursday to MasterCard Chief Executive Officer Ajay Banga asking for more information about charges the company levies on card issuers when purchases made with one of its brands are processed by a competing network.