Play by the FCC's rules or pay the price. That's the lesson learned by T-Mobile on Friday. The Federal Communications Commission (FCC) said that it is fining T-Mobile $17.5 million for a 911 service outages that weren't reported appropriately.

The FCC said that more than 27,400 calls are placed hourly to 911 call centers across the nation, and that T-Mobile's two separate outages on August 8, 2014 lasted about three total hours. That meant more than 50 million T-Mobile customers around the U.S. couldn't have reached 911 in an emergency.

"In its investigation, the Enforcement Bureau found that T-Mobile did not provide timely notification of the August 8, 2014, outages to all affected 911 call centers, as required by FCC rules," the FCC said. "The investigation also found that the outages would have been avoided if T-Mobile had implemented appropriate safeguards in its 911 network architecture."

The FCC has asked T-Mobile to identify and protect against possible risks, find a way to detect 911 outages, contact 911 call centers in affected areas and fix outages "on a timely basis."

Scary stuff, and while it seems nationwide outages aren't that common, it's frightening to know that consumers wouldn't have been aware that 911 wouldn't have worked during T-Mobile's outages.