The US telecoms regulator – the FCC – has announced it plans to fine AT&T $100 million for “misleading consumers about unlimited data plans and violating transparency obligations”.

Following an investigation the FCC is alleging “AT&T severely slowed down the data speeds for customers with unlimited data plans.” This wouldn’t be a problem if AT&T had told them it would do this but, apparently, it didn’t.

AT&T got into the ‘unlimited’ game way back in 2007 and while it doesn’t offer such tariffs to new customers now, it does renew old ones. In 2011, the FCC says, AT&T implemented a policy that throttled the data speeds of these subscribers after they’d passed a data threshold within the billing cycle. AT&T stands accused of insufficiently communicating this policy to ‘unlimited’ tariff subscribers.

“Consumers deserve to get what they pay for,” said FCC Chairman Tom Wheeler. “Broadband providers must be upfront and transparent about the services they provide. The FCC will not stand idly by while consumers are deceived by misleading marketing materials and insufficient disclosure.”

“Unlimited means unlimited,” said FCC Enforcement Bureau Chief Travis LeBlanc. “As today’s action demonstrates, the Commission is committed to holding accountable those broadband providers who fail to be fully transparent about data limits.”

In what is surely not a coincidence, Sprint has announced it will stop similar practices and this all seems to coincide with new net neutrality laws. AT&T is, of course, expected to dispute this allegation and fine.