AT&T has quietly begun offering microcells to some iPhone customers in hopes of keeping them from defecting to Verizon. Some readers have reported receiving e-mails from AT&T with the microcell offer "as our way of saying 'thank you' for continued loyalty," though not all AT&T iPhone users have received it.

The e-mail offer comes with a bar code and has instructions to visit an AT&T store to receive a "free" 3G microcell, which retails at $199.99. The microcell, which is actually a femtocell device, acts as a sort of 3G signal extender and allows you to receive a cellular signal on your phone in small areas—such as your home or office—where you might not normally get signal. (The femtocell device actually creates new 3G signal using your own broadband connection, so it doesn't really "boost" signal so much as it creates new signal.) AT&T first started selling its own microcells to customers last year and they have been moderately popular among those who live in low- or troubled-coverage areas.

There are few catches that come along with the deal, though. For one, customers who choose to accept the $200 device must stay on board with AT&T for another 12 months. Additionally, customers must either return the device to AT&T or pay for it at a pro-rated cost if they cancel their contracts before the 12-month period is up. Luckily, however, the carrier says the microcell agreement won't affect your ability to upgrade your handset or your contract end date, and some customers who have already cashed in on the offer reported that there were no hidden charges that came along with it.

AT&T hasn't formally announced the microcell offer, indicating that it's only being extended to select customers. The criteria for discerning who gets a microcell and who doesn't isn't very clear, but some believe it's going out to iPhone users who are at or near the end of their contracts. (AT&T did not respond to our request for comment by publication time, so we were unable to confirm this theory.)

This would make the most sense, though, as those are the customers who are most likely to switch to Verizon after the device makes its debut on that carrier come February 10. After all, the Verizon iPhone not only sold out within the first two hours of preorders this week, Verizon now says that those sales exceeded the one-day totals of any other device debut in Verizon's history. It's likely that AT&T is willing to go to great lengths to keep its current customers around, so if you're an AT&T customer who's feeling lucky, you may want to give the company a ring.

Update: It appears as if this offer isn't just limited to iPhone users after all as our original reporting said. The offer still isn't being extended to all AT&T customers, but it's being made available to subscribers who don't own iPhones as well.