AT amp T whose ownership of the DirecTV satellite service makes it the biggest U S pay television provider said late Wednesday it will report a third quarter loss of 390 000 satellite and cable customers echoing a similar warning weeks earlier from Comcast Corp The same night Viacom cautioned that its distribution deal with Charter Communications Inc the second biggest cable U S company may lead to a blackout potentially testing whether millions of viewers are willing to go without MTV and Nickelodeon 