carrier unlock via hardware

So I have a phone locked the 3 network in the UK. I checked this with apple and with 3, which they both confirmed. However, despite trying a few different sims from 3, I can't activate the phone, it just keeps telling me that the sim isn't from a network for the phone. I've also tried sims from pretty much every other uk network provider to be sure as well.

So I suppose at this point, I'm wondering if there's something in the hardware I can change to make it unlocked?

Any help would be massively appreciated