Battle to blacklist

In Jan 2020 we bought devices at vodacom they were running a promotion we got two phones and a tablet which came with 1 Sim card. At no point we were told using Voda Sim is a must so my wife used her telkom Sim card on one of the cell phones so now the phone is lost we trying to black list it and get itc number for insurance purposes they refuse to help and when we call telkom they say they don't have access to black list the phone as the iMEI belongs to vodacom. The consultants are so rude and not helpful at all. What's the best way to black list all I want is ITV ref no to claim from insurance.