LTE is starting to become a reality for prepaid customers on inexpensive plans. Straight Talk, a carrier formed from a partnership between Walmart and Tracfone, is now allowing users who bring smartphones capable with AT&T's LTE network to use the 4G data service. You'll need to buy a new SIM card for $6.99 to get the service, but once you do, you'll get "unlimited" data, talk, and text for $45 per month (or international calling on top for $15 more per month). And unlike some other services, you'll be able to use a device purchased directly from AT&T that's still locked to the network on Straight Talk. Of course, most phones purchased from AT&T come with a two-year contract — you'll need to complete the contract or pay an early termination fee to switch.

Straight Talk is a type of carrier known as an MVNO (mobile virtual network operator), which means that it doesn't run or own a wireless network. Instead, it purchases the right to use towers from AT&T, T-Mobile, Verizon, and Sprint. There are two primary reasons why one would choose prepaid cellular service: low price, and no long-term contracts. Traditionally, the drawback to such affordable service is that you can't use LTE service, you're stuck with older devices, and coverage can be spotty. Now that LTE has matured a bit and has proliferated across much of the country, it appears major carriers are willing to let MVNOs use the high-speed networks. Today's move by Straight Talk comes after AT&T opened up its LTE network to its own Aio Wireless prepaid brand, which the company is working to expand nationwide after purchasing another competitor in the space, Cricket Wireless. If you're considering making the switch, keep in mind that coverage can be rough at times, and "unlimited" isn't really unlimited as the carrier will throttle heavy users.