Roaming allows mobile wireless customers to automatically receive service when they are outside of the area covered by their provider's network. Mobile wireless service providers enter into roaming agreements with each other so that their customers will be able roam and receive service automatically, regardless of their location.
The FCC recognizes the importance of roaming for mobile consumers. In 2007, the FCC clarified  that wireless providers offering commercial mobile radio service (CMRS) must provide automatic roaming for voice, push-to-talk, and text messaging services - on a just, reasonable, and nondiscriminatory basis - to other technologically-compatible providers, but only in areas outside of where the requesting provider holds spectrum licenses.
In 2010, the FCC eliminated  that "home roaming exclusion" and required mobile wireless carriers to provide automatic voice roaming regardless of whether the carrier requesting roaming holds spectrum in an area. At the same time, the FCC sought comment on whether mobile wireless service providers should be required to provide for certain mobile data services, such as mobile broadband and Internet access services.In April 2011, the Commission adopted a requirement  that providers of commercial mobile data services offer data roaming arrangements on commercially reasonable terms and conditions, subject to certain limitations. With respect to any data roaming disputes, parties may file a petition for declaratory ruling under Section 1.2 of the Commission’s rules or file a formal or informal complaint depending on the circumstances specific to each dispute. Disputes would be resolved on a case-by-case basis taking into consideration the unique facts and circumstances in each instance and parties may be required by Commission staff to provide their best and final offers.
Consumer Fact Sheet  on Understanding Wireless Coverage Areas