AT&T introduces new Aio Wireless pre-paid service with plans starting as low as $40 a month
7GB with the Aio Pro plan. You can also add 1GB of data for an additional one time charge of $10 each month. If you have a tablet, the Aio tablet plan provides you with 250MB of high-speed data. Speaking of speed, the Aio service runs over HSPA+ and does not support 4G LTE.
You can bring your own GSM phone over to the plan buy paying $10 for a SIM card, or purchase a phone from the MVNO. The highest price phone available from Aio Wireless is the Samsung Galaxy Express, a dual-core handset with a 4.5 inch screen and 1GB of RAM for $250.
source: AT&T, AioWireless via AndroidAuthority