Sorry to hear about your mums sim there! Depends on the lock though! Do you know if it's PUK code locked? or some other type of locked? If it is the PUK lock, check this link here: http://www.vodafone.co.nz/help/mobile-phones/puk-code/ for steps to get that sorted if not, let me know a little more information about it and I'll see what I can do to help here!