News broke today that AT&T will likely charge iPhone users extra to use FaceTime video chat over cellular (3G or 4G) networks.

The change will take place once Apple's new mobile operating system, iOS 6, launches for iPhones and iPads this fall. Only the iPhone 4S and third generation ("new") iPad will be able to use FaceTime over cellular networks. (The next iPhone, which will likely launch around the same time as iOS 6, should be able to make FaceTime calls over cellular too.)

Here's the statement AT&T gave us regarding charging extra for FaceTime over cellular. We're pretty confident it's going to happen based on this:

We’re working closely with Apple on the new developer build of iOS 6 and we’ll share more information with our customers as it becomes available.

Again, we have example of carriers nickel and diming you for data you already own. Right now AT&T charges $30 per month for 3 GB of data. That's data you bought. With your money. Just like you buy candy or books or video games or gasoline.

But unlike when you buy candy or books or video games or gasoline, AT&T thinks it can tell you how to use your data. If I buy a gallon of gasoline, ExxonMobil doesn't charge me later for using it a different way. That's because it's my gasoline. I can use it to run my car or my motorcycle or my boat. Light it on fire. Whatever.

AT&T doesn't see cellular data that way.

AT&T's 3 GB plan lets you use the data to surf the web, check emails, stream video or music, and use apps that require data. But if you want to use your smartphone as a wi-fi hotspot, you have to shell out an extra $20 per month for that privilege. (That extra $20 gets you a total of 5 GB of data to use per month.) So even if 3 GB is plenty of data for you each month, you still have to pay a $20 premium to access the hotspot feature. If you only use 2.99 GB in a month, you lose the other 2 GB forever. (That's partly why Gizmodo advocates a rollover data plan, just like rollover minutes.)

I asked AT&T why all data plans aren't created equal. Here's what I was told:

To utilize a hotspot feature, customers will need to subscribe to the DataPro 5GB/$50 tethering data plan. Our other plans do not support the tethering feature. Many customers are likely to need that extra 2 GBs of data while tethering their mobile devices.

That's just bonkers. It's silly for AT&T to tell customer's when they're likely to use more data. For many the 3 GB plan would be enough. It's even more baffling considering AT&T will gladly charge you $10 for an extra GB if you go over your 3 GB allotment. The company is still getting your money.

Verizon doesn't charge you extra to use your phone as a hotspot. Verizon That's one benefit to Verizon's new shared data plans. You pay Verizon for your data and you can use that allotment on any device, any way you choose. It even works if you use your smartphone as a hotspot. This is the closest thing you can get to complete control over data you buy from a carrier.

According to 9to5 Mac, it looks like Verizon is holding on to that philosophy with cellular FaceTime usage on the iPhone.

AT&T should take note.