AT&T Corp. said some long-distance customers will get refunds as part of an anti-"slamming" settlement it reached with Business Discount Plan Inc. of Long Beach. AT&T filed its lawsuit against BDP in March in federal court in Illinois, accusing the company of using fraud and deception to switch customers to its service, an illegal practice known as slamming. BDP buys wholesale service from AT&T and resells it to customers under its own name and pricing. AT&T also accused BDP telemarketers of using the AT&T name to mislead and snare customers for itself. "We believe that Business Discount Plan was . . . charging customers up to three times the rates of their former telecommunications provider," said Carla Mascaro McEnroe, an AT&T attorney. BDP did not return phone calls. Under the settlement, the company must notify customers that it is not affiliated with AT&T. If customers want to switch back to their original long-distance company, BDP must make the change for free, AT&T said; in addition, BDP must refund the difference between its prices and those of the original long-distance carrier, AT&T said.