Small merchants have long chafed at the fees they must pay banks every time a customer swipes a debit or credit card. But now, with business slowing and every dollar important to their bottom line, some merchants are pushing for changes. The merchants are lobbying for legislation that would compel banks to negotiate fees with them and are supporting a second measure that its sponsors calls a "credit card bill of rights for merchants." At the same time, some merchants are seeking class-action status for litigation claiming antitrust violations by banks and the MasterCard and Visa card networks.