This column originally appeared on April 25 on Real Money, our premium site for active traders. Click here to get great columns like this.

Over the last five days, Verizon (VZ) - Get Report, AT&T (T) - Get Reportand T-Mobile USA's (TMUS) - Get Reportearnings reports have largely confirmed what many suspected: Verizon and AT&T's re-embrace of unlimited data plans have slowed down their share losses to T-Mobile, but haven't eliminated them. And their intensified efforts to hold onto their subscribers definitely has a price attached.

Last Thursday, Verizon reported it lost 307,000 retail postpaid wireless subscribers in the first quarter, well below a consensus analyst estimate for a net gain of 209,000 subs and a sharp reversal from the 640,000 net adds reported for the year-ago period. Moreover, 289,000 postpaid phone subs were shed, a reversal from the year-ago period's 8,000-subscriber gain. 17,000 prepaid subs were also lost (slightly better than expected), and total retail churn grew to 1.39% from 1.23% a year ago.

On Tuesday afternoon, AT&T reported 191,000 Q1 wireless postpaid net losses, a little worse than a consensus for a 127,000-subscriber loss and a reversal from the year-ago addition of 129,000 subs. Ma Bell did manage to add 282,000 prepaid subs and -- thanks partly to strong connected car subscription growth, a space where it has emerged as the U.S. leader -- 2.57 million connected devices. But it also lost 582,000 reseller subs, and let go of 2.3 million subscribers when it recently shuttered its 2G network.

Notably, Verizon and AT&T both reported a postpaid net subscriber loss for the first time in recent history. One silver lining: Each company's performance appears to have improved after it rolled out unlimited data plans. Verizon says it had 109,000 postpaid phone net adds after unlimited plans launched; AT&T says it had 12.3 million unlimited subs at the end of Q1, up from 7.9 million at the end of Q4.

Regardless, T-Mobile is still taking share at a healthy pace. The self-proclaimed Un-carrier reported 914,000 Q1 branded postpaid net customer adds, down a bit from the year-ago period's 1.04 million but better than a consensus estimate of 825,000. And the company hiked its (arguably conservative) full-year branded postpaid net add guidance to a range of 2.8 million to 3.5 million from one of 2.4 million to 3.4 million.

T-Mobile reported 1.1 million net adds overall, with 1.3 million branded net adds partly offset by 158,000 wholesale losses. Branded prepaid net adds totaled 386,000 (below a 509,000 consensus), with churn rising by 17 basis points annually to 4.01%. But -- in spite of Verizon and AT&T's more aggressive pricing -- branded postpaid phone churn fell to by 15 basis points to 1.18%, a level T-Mobile calls a record low.

The contrast between the carriers' performances becomes starker when one looks at service revenue growth. T-Mobile's service revenue rose 11% annually to $7.3 billion. Verizon's wireless service revenue fell 6.1% to $15.8 billion, and AT&T's by 1.8% to $14.5 billion. The latter's connected device growth is helping offset its postpaid pressures.

In addition to subscriber losses, Verizon/AT&T's service revenue is getting stung by ARPU declines caused by their unlimited plan launches, as well as related promotions. Verizon's retail postpaid average revenue per account (ARPA) fell by $8.36 annually to $136.98. AT&T's postpaid average revenue per user (ARPU) fell by $2.29 to $52.77, with its postpaid phone-only ARPU dropping by $1.44 to $58.09.

On the other hand, T-Mobile's branded postpaid phone ARPU rose by $1.32 annually to $47.43, and in spite of AT&T/Verizon's recent actions, the company forecasts its branded postpaid phone ARPU will be "generally stable" in 2017 relative to 2016. The fact that T-Mobile's pricing has long been aggressive has allowed it to continue undercutting Verizon/AT&T (by and large) without enacting major price cuts...especially when one accounts for perks such as built-in taxes and fees and free or cheap roaming in many locales.

Sprint (S) - Get Reporthas also been undercutting Verizon/AT&T, but its financial position is much more precarious than T-Mobile's and its capital investments much lower. Whereas T-Mobile produced $1.4 billion in free cash flow (FCF) last year and expects strong FCF growth over the next three years, Sprint has only guided for breakeven adjusted FCF for the fiscal year ending in March, in spite of cutting capex to minimum levels. And the company's service revenue fell 5% annually in the December quarter. Its earnings arrive on May 3.

It should be noted that lower sales of phones -- often sold at a negative margin -- did prop up Verizon and AT&T's bottom lines last quarter, as did spending cuts. Verizon's wireless equipment revenue fell by 4.8% annually to $3.8 billion, with retail postpaid device activations dropping by 800,000 to 9.1 million. AT&T's wireless equipment revenue fell by 17% to $2.6 billion (said to be a record low), with its postpaid phone upgrade rate dropping to 3.9% from 5%. That could have implications for Q1 U.S. iPhone sales; Apple (AAPL) - Get Report reports earnings on May 2.

The recent launch of Samsung's Galaxy S8, together with an anticipated fall iPhone 8 launch, will likely cause equipment revenue to move higher. Eventually, Verizon and AT&T will need to stabilize service revenue to keep wireless profits from declining. And a comparison of their subscriber bases with T-Mobile's shows why the latter is having little trouble adding millions of subscribers, even as Verizon/AT&T are able to hold onto many high-end and business customers due to their superior networks.

Verizon now claims 108.5 million retail postpaid connections, and a modest 5.4 million prepaid connections. AT&T claims 77.3 million postpaid "subscribers and connections," and 13.8 million prepaid ones. T-Mobile, by comparison, only had 35.3 million branded postpaid customers at the end of Q1, along with 20.2 million branded prepaid customers.

And going forward, T-Mobile's recent purchase of $8 billion worth of low-band spectrum should do much to narrow the rural and in-building coverage edges Verizon and AT&T claim, which in turn puts it in better position to go after both high-end and rural subs. The company claims it obtained an impressive 31MHz of spectrum nationwide on average through the auction, and says phones supporting the spectrum are expected "as soon as this year."

To a large degree, Verizon and AT&T's pressures aren't because a rival has executed better than they have (though T-Mobile's execution has generally been solid). They stem from the fact that U.S. postpaid mobile ARPUs have been notably higher than those of most other developed markets, and a rival with enough scale and resources to compete is taking advantage of the opportunity.

That's a long-term problem that can't be easily mixed. And that, along with wireline revenue pressures, might explain why both Verizon and AT&T seem so hungry to lower their telecom exposure via acquisitions.

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