LOS ANGELES (AP) -- Elizabeth Paige Laurie's name was on a sports arena when a former University of Southern California roommate alleged the Wal-Mart heiress paid her $20,000 to do her homework. Now it isn't even on a USC diploma.Laurie, the granddaughter of Wal-Mart co-founder Bud Walton, has returned her degree, nearly a year after Elena Martinez told ABC's "20/20" that she had written term papers and done assignments for Laurie for three-and-a-half years."Paige Laurie voluntarily has surrendered her degree and returned her diploma to the university. She is not a graduate of USC," the school said in a statement dated September 30 but not widely disseminated until the school newspaper wrote about it late last week. "This concludes the university's review of the allegations concerning Ms. Laurie."USC spokesman James Grant said Wednesday the university had no further comment. Laurie had been given a bachelor's degree by the USC Annenberg School for Communication in May 2004.After the homework allegations surfaced last November, the University of Missouri changed the name of what was then Paige Sports Arena.Laurie's billionaire parents, Bill and Nancy Laurie, had received naming rights in exchange for donating $25 million toward the building's construction. Nancy Laurie is Walton's daughter.A call seeking comment from Bill Laurie at his Paige Sports Entertainment company was not immediately returned. The family has repeatedly declined to comment on the cheating allegation.Martinez has an unlisted phone number and could not be reached for comment.At the time of the "20/20" broadcast, Martinez said she dropped out of USC because she couldn't afford the tuition. She said she learned a great deal by doing Laurie's class work.Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.