Question [Q] Returned from factory with KNOX - what do I do?

Hi everyone, I just had my phone repaired at the factory, sent in with a stock T-Mobile 4.2.2 ROM, but came back with KNOX.

I HAVE NOT booted the phone up -- I put it into download mode only to see the KNOX flags. But it's probably been booted before for testing at the factory.

Is there anything I should/can do before I turn it on normally (to help with ridding myself of KNOX problems)?

Eventually, I want to root it and/or install a custom ROM.