Hold onto your wallet if you're with two of the most popular Big 4 cell phone providers. AT&T is following a similar path to Verizon by offering a new rate structure that could make smart phone use much more expensive.

Under AT&T's Mobile Share program, you buy a block of data that can be shared across several devices, very similar to Verizon's Share Everything plan. You pay a monthly fee for each device and then you also pay for a block of data.

In essence, this puts tight caps on data. If you want more, you have to pay more. If you want a lot, you have to pay hundreds per month for the data portion of your bill alone.

Compare that to how the non-contract players like Straight Talk, Boost Mobile, Virgin Mobile, Cricket, and Metro PCS are doing business. Their entry level plans can range anywhere from $30 to $55 a month for unlimited text and data, and in some cases, unlimited talk minutes too. (Virgin Mobile and Cricket both offer the iPhone with no contract so you pay the full retail price for it.)

Not to mention the huge penalty fees you face for data overages with AT&T and Verizon.

So you can go with the Big 4 because you see their advertisements all the time, but watch out for your wallet! AT&T and Verizon customers, if you just let inertia carry you along and don't shop the marketplace, you're going to pay.

Editor's note: This segment originally aired July 18, 2012.