From which phone was the upgrade to premium was done!!!!!!!

Last year my father downgraded his account to Access and in December an upgrade was done to a Premium, I have been on calls with different agents trying to understand how the upgrade was done as my dad is not tech smart and he wouldn’t know how to do an upgrade like this on his WhatsApp as he only communicates via voice notes. I called yesterday and spoke to a Siphesihle who said she is one of the managers but refused to give her last name. She said she had escalated the case to your self service department to advise on which device the upgrade was done from, I am on a call with one of the consultants who just advised that there was no escalation that was done yesterday yet we are expected to pay the amount we know nothing off. I have been trying to sort out this for my dad since early this month and we are not getting anywhere with your team.