If Apple needed any help selling its new iPhone 7 line, mobile carriers may have come to the rescue. All four major carriers offered a free iPhone 7 to customers who traded in an earlier model and agreed to stay on for two years.

Now the results of the promotions are starting to trickle in. T-Mobile CEO John Legere, who was first to market with the trade-in offer, said iPhone 7 preorders hit record levels, totaling almost four times more that the prior record holder, the iPhone 6 in 2014.

“The iPhone 7 has been doing amazing at @TMobile!! Let’s talk about it!!” Legere said on Twitter, kicking off a series of tweets about sales of the new iPhone. Legere had first mentioned the record sales in a live talk on Periscope on Monday night.

Get Data Sheet, Fortune’s technology newsletter.

Apple shares were up 3% in midday trading on Tuesday on the news, even as the overall stock market declined. Shares of T-Mobile fell 2% along with other telecom stocks.

Now, as the fastest growing carrier, T-Mobile tmus also has a lot more customers now than it had two years ago. The carrier ended the second quarter with 67 million subscribers, up from 50 million two years earlier. But the increase in iPhone preorder volume was considerably higher than the customer growth.

Competitor Sprint s didn’t mention any records, but said preorders for the iPhone 7 over the first three days were up 375% from last year’s preorders for the iPhone 6S in the same period.

As of Tuesday morning, the two other major carriers, Verizon vz and AT&T t , had yet to make any comments about their preorders.

For months, Wall Street analysts who follow Apple aapl have been warning that sales of the iPhone likely would not match last year’s sales. The new model has an almost unchanged exterior design and lacks a sufficiently compelling new feature to attract hoards of current iPhone owners to upgrade, the analysts have said. And smartphone owners in general have been holding onto their devices for longer since the carriers have phased out subsidies.

But the carrier promotions may have changed the equation. All four carriers have made the free with trade-in offer, with only slight variations. A customer who trades in an iPhone 6 or 6S gets an iPhone 7 with 32 GB free as long as they stay with the carrier for the next two years (if they leave early, they have to pay a prorated share of the iPhone’s $649 price).

Apple itself said it would not be providing first weekend sales, as it did in the past, magnifying the importance of the carrier reports, according to analyst Brian White at Drexel Hamilton.

“Given that Apple will not be releasing opening weekend sales for the iPhone 7/7 Plus, investors will be searching for any incremental information that provides color around the strength of this cycle,” White wrote in a report on Tuesday. “We are very encouraged by these strong pre-order reports from T-Mobile and Sprint, combined with the best August ever for our Apple Monitor that we discussed last week.”