[Q] Why is APN locked?

Hi

I am helping out a friend with his Lenovo K3 Note which he imported from Asia

The phone is unlocked and we changed the APN's earlier. We rooted it, removed some bloatware and now after a few days he comes back and there is no mobile data signal available.

I know it probably has to do with something else, but my main problem is that the APN is locked, even though it wasn't earlier.

How do I delete it?

Thanks in advance