Though this situation seems impossible to me to begin with, to get the
phone reset you'll need to go to a Sprint Corporate store and have
them do it. Otherwise, RadioShack might be able to send it off for you
to get reset. I think it'd cost you about $25 overall.

Bit of an old phone though.

If you have Sprint's master subsidy lock for the i330, you can try
taking the phone into a Sprint store and see if they can reflash the
phone with Sprint's software/firmware.