Was on Boost, Sprint says they can't use it now...
I bought my phone from a reseller (NEW) a few years back and this phone was rooted and unlocked to run on Boost Mobile.
I recently re-flashed the stock ROM back on it and factory reset the phone, and gave it to a friend who wants to run on Sprint.
He took it to the Sprint store and they said it is "locked to Boost Mobile" and they cannot use it??!?
I'm really confused as it is "unlocked", which means I should be able to run on any supported (same technology) carrier.
What do I need to do to be able to use this on Sprint's network once again?