AT&T wants to get some of its existing users to upgrade a bit earlier than before by offering AT&T Next contracts to its subscribers after six months.

Starting today, anyone who signed an AT&T contract before January 18, 2014 can “upgrade” their standard contract to an AT&T Next plan after six months. Those who started a contract on Saturday will have to wait until July 18 to take advantage of this new offer. Those who signed a new contract since then are stuck with their phones for the next 20 months, and contract for the next two years. Unless you take up John Legere on his offer, that is.

AT&T Next, you may remember, is AT&T’s answer to T-Mobile’s early Uncarrier moves. The plan lets subscribers get a phone for $0 down and pay it off over the course of the next 20 months. It’s also an early upgrade plan, letting users trade in their phones for a new one once every 12 or 18 months instead of every two years.

The plan sounds great, unless you think about it for more than the time of a 30 second commercial. While AT&T’s Next plan does let you upgrade once every 12 or 18 months, you end up paying more for the privilege. AT&T Next adds the cost of the smartphone to the cost of a Mobile Share Plan that typically lasts for two years and already includes phone subsidies. Then, after paying extra for the phone, you have to turn it into AT&T for the chance to pay more money for your next phone.

Under a typical contract you get to keep your phone when you upgrade. That means you get to sell the phone, recouping part of the cost. AT&T Next doesn’t let you do that.

Extending AT&T Next to existing customers is an obvious ploy by AT&T to prevent long-time subscribers from switching to T-Mobile. At CES T-Mobile CEO John Legere announced that his carrier will buy out the contract of anyone who switches to the magenta network. The CEO’s Twitter stream is now full of new customers proudly displaying their carrier break-up letters. In the first week more than 80,000 carrier break-up letters were posted to various social networks.

With its Jump insurance plan and friendly attitude towards unlocked devices, T-Mobile is currently the carrier of choice for those who like to upgrade their phones more than once every two years. It’s hard to see AT&T or any other carrier competing on that front without some massive changes.

Will AT&T’s offer entice you to stay? Or are you looking to switch to T-Mobile in the near future?