My parents were both sent new sims as part of your sim swap. My mum changed hers with no problem, but my dad's phone has now been locked for weeks!!
He has an old Sony Ericsson J100i, I believe there was a code with the original letter, but that didn't work and the sim was immediately locked. My mum was able to get through to someone on the phone, who sent a second replacement sim but the code also did not work with this one. The phone was saying 'Sim card locked. Please contact your network', but after receiving a new unlock code by filling in the online form I thought this maybe corresponded with the first replacement Sim, so I tried swapping them to no avail. Phone is now asking for subsidy password again!!!
I think this is utterly ridiculous and my dad has now been without his phone for weeks!!!! It seems ludicrous that you have caused such a problem for so many people. I would appreciate someone coming back to me with a resolution as soon as possible!!