Websites like Celltradeusa.com and cellswapper.com are becoming popular destinations for users who want to avoid paying an early termination fee when switching carriers. Both services charge about $20 to hook mobile subscribers up with another user to bid on someone else's contract. Article [1]
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[1] http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2007/08/20/BU2ERJUER.DTL&type=tech