T-Mobile has today announced Un-carrier 8.0, introducing its new personal Data Stash feature for subscribers. This new Data Stash will enable anyone who doesn't use up their data allowance for that month to store this remaining balance on their T-Mobile account for use another time. Put simply, you'll be able to automatically save the remaining data allowance each month for free, and then use this hidden stash whenever you run over the limit.
Full story from the WindowsCentral blog...