As cellular carriers evolve over time to accommodate new technologies, certain phones are being left behind; T-Mobile is about to discontinue support for nearly 20 handset models.

There is some good news, though. The devices on T-Mobile's list are quite old. And the carrier is apparently helping affected customers by offering new phone options.

All of this comes on the heels of T-Mobile's January decision to discontinue support for phones that cannot use Voice over LTE (VoLTE) service; according to Android Police, T-Mobile's internal document states that on January 29, support will be discontinued for According to Android Police, internal T-Mobile documents list 19 devices, including phones, tablets, and cameras, that will be unsupported on January 29. The impacted devices include the Samsung Galaxy Note Edge (AT&T and Verizon versions), Google Nexus 9, Huawei Mate 8, HTC Desire 10 Lifestyle, and four different Sony Xperia Z3s.

Most of the devices on the list appear to be at least five years old, so it's time for an upgrade anyway. And apparently, starting on December 28, T-Mobile will be contacting customers who have these phones to let them know that they can grab a free upgrade from the carrier.

Specifically, these customers can replace their aging phones with a choice of the Samsung Galaxy A21, Samsung Galaxy A11, Alcatel Go Flip 3, or T-Mobile Revvl 4. These phones are not exactly state-of-the-art, with prices ranging from $100 to $250, but at least customers are not obligated to do the upgrade themselves.

The promotional period for the free upgrade ended yesterday (December 24, 2012; the first day of the free upgrade period was December 24, 2012). However, not all customers are eligible for the free upgrade. If you're likely to be affected, it's worth contacting a T-Mobile store or representative to ask if you can participate in the promotion.

Some customers may receive an offer of $150 off a new phone instead if they decide to purchase a new device from T-Mobile. Reportedly, T-Mobile employees have been advised to "stay tuned" for additional promotions that are "specifically targeted" to affected customers.

According to Android Police, T-Mobile says that the campaign is not related to the end of support for non-VoLTE devices, but it seems very convenient given that certain customers with the devices are being targeted for upgrades.T-Mobile has yet to make an official announcement regarding the upgrade program and has not confirmed which customers are eligible.