T-Mobile has been on a roll for a long time. CEO John Legere said it would take over Sprint and now it has. T-Mobile Leaps Over Sprint To Become The #3 US Carrier. The wireless un-carrier has done this in terms of the number of its customers. According to Legere, Sprint's customer base has stayed the same for the past two years with 55 million customers, while T-Mobile has experienced a massive amount of customer growth. He also said that Sprint is cooking the books by using some inactive MVNO customers when reporting on its customer base. T-Mobile's lead over Sprint should become clearer by the next quarter or two.