said by TKJunkMail :

I just don't see AT&T sitting still for this company's customers running unlimited data over the AT&T network and the company paying minimal fees to AT&T. I see a lengthy lawsuit in their immediate future.

said by »www.pcmag.com/article2/0,2817,2342994,00.asp :

The phones run on GSM networks including AT&T's and T-Mobile's. But Zer01 isn't buying time wholesale from AT&T and T-Mobile, Piilani said. Instead, they have purchased their own IP backbone and are using interconnect (AKA roaming) agreements, the way Verizon and Sprint phones work on each other's networks. Each device on the Zer01 network gets a fixed IP address and opens a VPN tunnel to the company's servers, Piilani said.

"It's our own VPN, and we're actually providing the data the customer is using," Piilani said.

By using interconnect agreements, Zer01 can get around the carriers' 5GB/month data caps and offer truly unlimited data, Piilani said. The company's system does some traffic management to make sure that heavy users don't overload a local cellular system.

said by elias :

RTFA...

I read the article wise guy. But maybe you don't understand how AT&T will respond. The method that Zer01 is using results in less income and higher costs to AT&T. Some companies tried to use interconnect agreements once before for those free conference calls and used the revenue splits to stiff AT&T. It was within the regulations, but AT&T and other carriers just shut them down anyway.