Good luck with that. Sprint or any prepaid carrier associated with them will do no such thing.
In my particular case with a Boost phone, I'm not sure if they keep it catalogued or what, but it comes up flagged as subsidy locked even if I try using it on Ting Mobile (On a prepaid phone, that's hilarious). I've begged and pleaded with Sprint before, and no dice. Their CSRs are previous Capital One employees