It seems like everyone is going "un-carrier" these days, slowly branching out from the standard two-year contracts that have dominated the US smartphone industry for the last few years. Today AT&T announced a new "Mobile Share Value Plan" for families and small businesses, which gives both new and existing AT&T customers the opportunity to share unlimited talk and text and a 10GB pool of data starting at $130 a month. AT&T's pricing table indicates that you'll be paying $100 for the 10GB of data and $15 for each phone you connect—three lines will run you $145 a month, four will cost $160, and so on up to a total of 10 lines for $250 a month.

New-to-AT&T customers who want to take advantage of the new pricing will either need to sign up for AT&T's Next program, bring their own unlocked devices, or buy phones at the standard unsubsidized price. Next program customers pay nothing up-front for new phones but need to pay the full unsubsidized price of their phones in monthly installments. The cost of these installments isn't included in the Mobile Share pricing table above.

Whether AT&T's plan will actually save current customers any money depends on your specific situation. I personally am on an AT&T MobileShare plan that gives the two iPhones on it unlimited talking and texting plus a pool of 6GB of data to share, and our two-year contracts won't be up for renewal for another 20 months. Each phone currently costs $40 and the data costs $80, for a total of $160 (plus other account fees). We could save $30 a month by switching to the new 10GB plan and gain 4GB of extra data to use to boot—by the time our contracts were up, we'd have saved approximately $600. If we were on the current 10GB Mobile Share plan, we'd be saving $50 a month, for a total of about $1,000. We'd be on the hook to join AT&T Next or buy unsubsidized phones when our contracts were up though, and assuming we both bought high-end phones we'd end up paying around $600 per phone rather than the $200 per phone we'd pay with the current subsidized pricing model. The closer you are to your contract's renewal date, the less you'd stand to save by switching if you upgrade as soon as your contract is up, though obviously you can choose to defer and keep your existing phone longer if you'd like.

Obviously this will differ for you if you opt for cheaper unsubsidized phones like the Moto G, the Lumia 520, or even the Nexus 5, if you choose to wait longer to upgrade your phones, or if you're planning to jump ship from AT&T the next time your contract is up for renewal anyway. The moral of the story (as it so often is) is that you need to pay close attention when signing up for any new plan from any of the wireless operators in the US. It's definitely possible to save money, but often the cash you save each month will be replaced by larger up-front upgrade fees for phones.

AT&T will begin offering the plans to new and existing customers tomorrow.

Update: Now that the plans are live, we can see a little more pricing information for plans above and below 10GB of data a month. The plans to the right are for two smartphones—add $15 for each additional phone you'd need.

An AT&T representative told us that all 10GB-and-up Mobile Share plans were being replaced by the new pricing structure. All plans using 8GB or less of data will still use the previous Mobile Share pricing, and won't require you to use AT&T Next or bring your own phone.