In advance of Verizon's (VZ -0.64%) releasing its quarterly earnings Tuesday, T-Mobile (TMUS 0.83%) CEO John Legere released a blog post trolling his rival with talk of midlife crises. This taunting been a steady Legere tactic that has worked even though Verizon CEO Lowell McAdam rarely responds. The T-Mobile boss takes to the internet, says some incendiary things about Verizon (and/or AT&T (T 0.09%)), and then sits back watching his message get spread.

It's a tactic that has aided in the addition of over 1 million T-Mobile customers each quarter for over three years. In addition, T-Mobile's Un-carrier strategy, which has involved dropping contracts, eliminating overage charges, and now rolling all fees into the advertised price, appears to be hurting Verizon. In the just-reported Q4 results, the company is making less money on its post-paid customers even though those users now have more connected devices on average.

Legere has been very aggressive when it comes to attacking his rivals. Image source: T-Mobile.

What did Legere do?

T-Mobile's stated goal with Un-carrier has been to not only lower its own prices and get rid of hidden charges for its customers, but to force the whole industry to do so. Verizon has begrudgingly followed along in some cases, dropping contracts, for example, and changing its overage policies.

In this latest blog post, Legere accuses Verizon of being at the peak of a midlife crisis. He also mocks the company's new rate plan that offers consumers 5GB of data for $55 a month.

"In a fit of nostalgia for their better days, Verizon last week introduced a new limited plan, and they're spending millions advertising that their network is perfect for people who accept data limits," he wrote. "I couldn't agree more. Verizon's network is perfect for limits. T-Mobile's network is built for people who want to be unlimited."

Legere is mocking the idea Verizon pushes that since many people don't currently use more than 5GB, there is no reason for them to have an unlimited plan. That's a concept the T-Mobile CEO finds outdated now that his company only offers unlimited plans.

"The ship has sailed on this one. Limits suck," he wrote "Asking someone how much Internet they want each month is ridiculous. We're pushing the industry past this outdated practice."

How is this hurting Verizon?

T-Mobile's efforts have forced Verizon and AT&T to be a little more customer-friendly. For Verizon this has meant dropping contracts and adding something called Safety Mode. The feature lets customers opt-in to have their data slowed down when they exceed their monthly allotment. Verizon does not say how many users have opted-in to use this feature, but the fact that it exists can be attributed to T-Mobile.

The Un-carrier has not crushed Verizon. The No. 1 carrier still holds its spot, but it's beginning to look like T-Mobile might eventually cause its death by a thousand paper cuts.

Verizon saw its service revenue -- basically money earned from providing wireless services -- drop 5.4% from $70.39 billion in 2015 to $66.58 billion in 2016. Even with an undefined "other" category rising by 16.8% from $4.36 billion to $5.09 billion, overall wireless operating revenue (which also includes an equipment line) dropped by 2.7%.

The loss occurred largely because Verizon now makes less money per post-paid customer. Average revenue per postpaid retail account (ARPA) dropped to $144.32 in 2016 from $152.63 the previous year. That's also a 5.4% drop and even more damning is that ARPA fell even though the company has seen more connections -- an average of 3.07 in 2016, up from 2.98 in 2015 -- from its postpaid customers.

Verizon is facing a crisis

These numbers are not awful, but it shows that the wireless industry has fundamentally changed. Verizon has lost sources of revenue -- specifically some overage charges -- that it won't be able to make up. In addition, with T-Mobile now rolling fees into its advertised pricing, Verizon will face pressure to if not do that, at least be more direct in its pricing.

The days of selling a data plan and then charging a "line access fee" to actually use that data are coming to an end. Verizon has to be able to see that and while Legere teases Verizon about wanting to bring back the good old days, McAdam must realize that you can't put the genie back in the bottle.