Americans get a raw deal on the cost of mobile calling and data services compared to the rest of the world. With the average monthly phone bill now at over $80 per month and high roaming charges for anyone traveling internationally, U.S. mobile phone users pay much more than their counterparts in the U.K. and Europe.

But Unreal Mobile, a new offshoot brand from popular mobile virtual network operator (MVNO) FreedomPop, today announced that it is now formally offering AT&T SIMs that will work on any unlocked GSM phone. Unreal has already delivered low-cost mobile services to over 50,000 people, but until today only certain Sprint devices worked with the service and most of those did not qualify for the MVNO.

“In the U.S., carriers make tens of billions in revenue,” FreedomPop CEO and founder Stephen Stokols told me. “As network costs have come down the past several years, carrier average revenue per user (ARPU) is actually up slightly, as the move to unlimited plans has resulted in lower-usage consumers forced to pay for unlimited [plans]. Unreal Mobile leverages unique carrier agreements to be able to offer the tiered unlimited plans — starting at 80 percent less than large carriers. For $10 a month, Americans can get an unlimited plan with Unreal Mobile.”

Previously only available through the Sprint CDMA network, Unreal now delivers a low-cost, unlimited mobile and Wi-Fi service through AT&T’s GSM network, which opens up the possibility for the MVNO to provide full spectrum coverage to users across the U.S.

“Users get unlimited talk, text, and data,” Stokols said. “In addition, Unreal Mobile users get a suite of value-added services, including Wi-Fi calling, the ability to leverage an OTT app and access your phone from any device or tablet, and a free VPN for secure private browsing.”

That helps make a significant dent in any consumers‘ phone bill, though Unreal Mobile isn’t quite ready for international users at present.

“UNREAL Mobile plans include international calling,” Stokols said. “International Roaming isn’t included,” however.

That might be a deal breaker for some, but travelers can always use devices such as the Skyroam Solis to access unlimited data in 120+ countries at a low additional cost.

So what’s next for Unreal Mobile?

“With the launch of the Unreal SIM, Unreal is no longer constrained by having to hold device inventory,” Stokols said. “It has already secured nationwide distribution deals with Target and Best Buy and expects to add hundreds of thousands of users over the next quarter.”

Unreal Mobile customers have the option to purchase an AT&T SIM to use with their current smartphone for $4.99 or to purchase a smartphone directly through Unreal Mobile, with models starting as low as $49. Mobile hotspot users can purchase a device for $20, with plans starting at $10 a month for unlimited data.