Nwtwork lock an unlocked SIM

Hi all,

Have an interesting question. I bought an unlocked S4 on ebay and found that it was not factory or paid unlocked, but by first rooting then unlocking the network. And this was after I paid for unlocking lol oops. I emailed the seller and he confirmed the root/unlock, but that he doesn't remember how or what he used, yeah right.

Is there a way to undo the sim unlocked phone via root?

I just barely finished returning to stock after several days of stuck on firmware recovery fail.

Thanks

SCH-I337, running 4.4.2, NB1