Good move, Ralph! There's no doubt about it. Today, AT&T decided to punish some of its most loyal customers by effectively killing their unlimited data plans.

Here's what happened.

There have been various reports over the last few months that AT&T was intentionally slowing data speeds for customers with unlimited data plans.

Why?

Because AT&T began a new policy a while ago that stated it would start throttling data speeds for unlimited customers if they were in the top 5 percent of data users.

But then some customers started getting notices that their data speeds would be throttled even though they hadn't even passed the 2 GB mark. To put that in perspective, AT&T's current tiered plans for new customers cost $30 per month for 3 GB of data. That's the same price unlimited customers pay but the tiered customers were getting a whole gigabyte more at full speed.

Obviously, the unlimited customers felt pretty screwed. Why were they paying $30 per month for "unlimited" data when they were being slowed down before they even reached the cap for customers on the tiered plan?

AT&T's answer was to introduce a new policy that effectively kills its unlimited data plan for good. If you're on an unlimited plan with a 3G or 4G HSPA+ phone, AT&T will start slowing your data once you use up 3 GB in a billing cycle. If you're using one of the fancy new 4G LTE phones with super fast data speeds, you'll get a slightly better deal. AT&T will start throttling 4G LTE customers after 5 GB of data usage.

Technically, AT&T is keeping its promise to unlimited customers. You won't be charged a cent if you go over 3 GB. You'll just experience slower speeds.

Sneaky!

Here's what that all means: Starting today, AT&T is going out of its way to completely screw over some of its most loyal customers. The reason why there are so many customers on unlimited plans is because they're grandfathered in every time they renew their contract with AT&T. They've stuck with AT&T for years and years.

I'm one of those customers. Part of the reason I've stuck with AT&T all this time is because I got to keep my unlimited data plan. I was tempted to switch carriers once Verizon got the iPhone, but that would've meant signing up for a tiered plan. So I stayed on AT&T.

Now I have no reason to be an AT&T customer. As soon as a killer new smartphone launches on Verizon (maybe the iPhone 5?), I'm going to make the switch. Over the years, AT&T has delivered horrible service in New York. Slow speeds. Dropped calls. Bad connections indoors. You know, all the normal complaints people have with AT&T.

The promise of unlimited data was the only thread keeping me tied to my AT&T contract. Now it's time to cut it.