T-Mobile didn't want its rural users to know how shitty its service was, so when the company couldn't connect a call, it would play fake "ring tones" to the caller that made it sounds like the person on the other end wasn't picking up. It did this "hundreds of millions of times" per year.
The FCC has fined T-Mobile $40,000,000, but will not require the company to issue refunds to the customers it scammed.
T-Mobile had engaged in this practice for years, and then the FCC banned it, but they didn't stop. Hence the fine.
The FCC order explains that T-Mobile has been using fake ring tones for a decade. In 2007, T-Mobile "began using servers that included a 'Local Ring Back Tone' (LRBT) for calls from certain customers that took more than a certain amount of time to complete," the FCC said.
When T-Mobile migrated to different servers in 2013, the carrier "began using the LRBT only for the out-of-network calls from its customers that were routed via Session Initiation Protocol (SIP) trunks and that took more than a certain amount of time to complete," the FCC said.
T-Mobile acknowledged that it "continued its practice of using the LRBT on such calls (and expanded the LRBT to cover such calls on additional SIP routes) after the FCC rule prohibiting the practice went into effect in January 2014," the FCC said. "Because T-Mobile applied this practice to out-of-network calls from its customers on SIP routes that took more than a certain amount of time on a nationwide basis and without regard to time of day, the LRBT was likely injected into hundreds of millions of calls each year."
T-Mobile deceived customers with “false ring tones” on failed phone calls [Jon Brodkin/Ars Technica]