Warren Buffett has invested in all three major U.S. wireless carriers, but Berkshire Hathaway (NYSE: BRK.A) (NYSE: BRK.B) currently owns just one. T-Mobile (NASDAQ: TMUS) has outlasted its peers AT&T (NYSE: T) and Verizon (NYSE: VZ) in Buffett's portfolio. Berkshire bought AT&T in mid-2015, only to turn around and sell it in the next two quarters.