On Monday, AT&T will announce the availability of the eagerly awaited Nokia Lumia 900, a high-end yet inexpensive device that the company’s sales agents are allegedly drooling over internally. Selected as Microsoft’s premier carrier partner for Windows Phone, AT&T sells more of these handsets than any other company. And yet, as I promised Microsoft before its latest mobile platform launched, this carrier has done nothing but disappoint Windows Phone users again and again, delaying and sometimes refusing to ever release valuable software updates. If that’s how Microsoft’s “premier” partner behaves, how will this platform ever survive?

The latest AT&T/Windows Phone uproar involves the Windows Phone 8107 update, which was rolled out by Microsoft in the first week of January. This update includes fixes for several bugs, including a common one in which the on-screen keyboard inexplicably disappears while you’re typing. Other fixes include Gmail syncing and location access, among others. It’s exactly the type of fix that all Windows Phone users should get automatically.

Except that that’s not how Windows Phone works. As I explained in Windows Phone Software Updates Revisited, there’s been a lot of confusion about how and when wireless carriers can block software updates from reaching end users. And the answer, it turns out, is that carriers can block updates whenever they want to. AT&T, somewhat surprisingly, has been the most aggressive about doing so. In fact, it’s never immediately delivered a Microsoft software update to customers. Not once.

As Microsoft’s Eric Hautala wrote at the time, the 8107 update is “available to all carriers that request it.” AT&T has obviously not done so. And as of this week, it appears it never will do so. “We are not currently planning to offer the Windows [Phone] 8107 update,” an AT&T community manager wrote in the company’s support forums in response to numerous complaints.

I’ll remind readers that AT&T is Microsoft’s premier partner for Windows Phone ... that this carrier had a bigger selection of handsets at the system launch in late 2010 than any other carrier .. and that AT&T has an exclusive month-long lock on LTE-based Windows Phone 7.5 handsets that extends to mid-year. That latter arrangement angered AT&T’s chief rival, Verizon Wireless, so much that its CEO threatened to abandon the platform until LTE devices were made available. And as of today, Verizon not coincidentally sells only a single Windows Phone handset, the out-of-date Trophy model it first began selling in early 2011.

I’ll also remind Microsoft that I told you so. In an October 2010 reviewer’s workshop at which I was warned that an AT&T representative was present, I told Microsoft and that representative that AT&T and the other carriers would have no qualms about blocking software updates in order to sell new phones. And I was told in return that I didn’t understand the close nature of their relationship and that the wireless carriers understood that a good user experience was key to the success of the platform.

Well, that has certainly played out as expected. So I’ll just reiterate what I’ve said all along. We can't trust AT&T or the other wireless carriers to do the right thing, ever. The biggest success of the iPhone is that Apple was able to wrest control of the software-updating process away from carriers and put it in the hands of the users for whom these updates matter most. And iPhone users have been rewarded with a long string of free software updates that have enormously improved the usefulness of the devices over time.

Microsoft, too, has delivered a similar string of useful updates. Sadly, many Windows Phone users never get to see most of them. And the reason is that the carriers are evil—pure and simple. They don't act in the best interests of users; they act in accordance with their own lazy self interests. And it’s time for this to stop.

AT&T, I’d like my on-screen keyboard to stop disappearing when I’m typing. Microsoft fixed this bug in January, after putting that update through a series of tests that, get this, were partially designed by AT&T. There is no good reason for me and other Windows Phone users not to have this update already. No good reason at all.