Tracfone is already one of the larger mobile virtual network operators (MVNO) in the country, with some 18 million customers using the network it leases from T-Mobile and AT&T. Now, Tracfone's parent company América Móvil has announced it plans to purchase MVNO Simple Mobile for an undisclosed amount. Simple Mobile also leases network from T-Mobile, though it is a "SIM-only" service — customers are encouraged to bring their own device, though Simple does have a section of its site dedicated to helping visitors find a compatible handset. It's not at all clear yet what América Móvil and Tracfone have planned for Simple — we don't yet know if the Simple brand and SIM-only sales method will continue, or whether it and its one million customers will get rolled into Tracfone. The deal is expected to close sometime during Q2 2012, so we should get more details soon.