TelCel America is an MVNO that operates on the T-Mobile network with a focus on providing international calling particularly for those calling to Mexico. The MVNO does come with T-Mobiles roaming agreements with ATT as they operate on both the 850 Mhz and 1900 Mhz bands, so you should get good voice coverage at the least throughout most of the country. Plans start at $20 for a basic 7 day plan and go up to $60 for a monthly plan. These two plans are of particular importance for those that frequently travel to Mexico as each one provides roaming while visiting there. The $20 plan includes 250 minutes, while the $60 plan includes 1000 minutes. The weekly plan also includes 1 GB of high speed data, while the monthly has 2 GB. Other plans offered range in price from $29-$50 and all but the $29 plan include unlimited international calls to landlines, while the $29 plan is capped at 1000 minutes. Minutes to Mexico and Claro Guatemala are also included and go incrementally up from 100 to 1000 minutes as you move up each price point offered. A summary of TelCel America's plans can be found in the infographic below.
TelCel America isn't the only MVNO out there to focus on international calling. Several other providers such as LycaMobile, Ultra Mobile and soon Mariposa are also options. Español Mobile is also said to be working on international calling plans.