1. A method performed by a user device, the method comprising: downloading, by the user device, autodialer application from an application server, the autodialer application including summaries of plan features and respective terms and conditions associated with a plurality of prepaid calling plans corresponding to at least two different service providers and permitting a user, of the user device, to purchase a prepaid calling plan and make telephone calls using the prepaid calling plan; importing, into the autodialer application, one or more contacts from the user device responsive to a user selection, to form a contacts list including associated telephone numbers corresponding to destination user devices; concurrently presenting, via a user interface generated by the autodialer application, different ones of the plan summaries associated with different ones of the plurality of prepaid calling plans; receiving, responsive to the presenting, selection of one of the different ones of the plurality of prepaid calling plans; receiving, by the user device and via the autodialer application, an instruction to purchase the selected prepaid calling plan; receiving, by the user device and from the user, payment information to establish a prepaid balance associated with the selected prepaid calling plan; presenting, on a display associated with the user device, confirmation information when the payment information is received, the confirmation information including the prepaid balance and access information; receiving, by the user device, a request to make a call using the purchased prepaid calling plan, and retrieving, responsive to the request, the contacts list for use in generating a contacts user interface including a telephone number corresponding to a destination user device; calling, by the user device, the destination user device using the telephone number corresponding to the destination user device and the access information; determining, by the user device, a duration of the call to the destination user device; computing, by the user device and under the purchased prepaid calling plan, a cost of the call based on the duration of the call; and updating, by the user device, the prepaid balance based on the computed cost of the call.