Virgin Mobile USA plans to offer a new type of prepaid smartphone plan in the US that will allow you to change what you've selected mid-billing cycle and even get a refund for unused data or minutes.

The plan is all about customisation. You can select the smallest amount of minutes available just to keep your phone number active or you can go all-out and get a plan focused on social media, letting you post an unlimited amount of tweets and Facebook posts. You could even get a plan with a lot of data and no restrictions on audio streaming.

Called Virgin Mobile Custom, Sprint-owned Virgin Mobile USA said the plan would launch on 9 August exclusively at Walmart. It is limited to three $130-or-less Android phones (ZTE Emblem, LG Pulse, and Unify) at the moment but could extend to other devices in the future, according to Gigaom, which interviewed the president of Sprint's prepaid group.

Walmart in the US is known for selling a range of prepaid smartphones by different carriers, but the plans are often stifling. Customers can either select small or large amounts of minutes, messages, and data at a time, and they certainly can't change their mind about what they purchased mid-cycle and get their money back for anything unused.

A company that specialises in a new kind of carrier billing however, called ItsOn, is providing prepaid customisation services. Sprint recently signed a multi-year deal to license ItsOn. The service primarily involves an Android app that you can open at any time to set up or adjust a plan. You can select 1,000 texts initially, but later change that to 500, for instance.

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Voice minutes, messages, and data can all be tweaked separately and spread out over individual phones or up to five lines in a family plan. The app also comes with parental controls and special add-ons. You can use the parental controls to stop kids from running up your bill or the add-ons to get specific packs like an unlimited tweet add-on for $5 a month

Virgin Mobile USA said it would release more pricing details when the program kicks off next month.