UNAUTHORIZED UPGRADES... Poor service from Telkom with regards to Cell phone contract

I have three cellphone contracts with Telkom. Two of the three are on a month to month basis because the 24 months are complete. Telkom phoned me multiple times from the beginning of the year where I repeatedly kept on saying I'm not interested in getting upgrades. With my June invoice I saw one of my numbers being upgraded from 1GB to 6GB. I never authorized this number to be upgraded. I've been phoning telkom since the day I received my invoice on the 5th of June but they keep telling me they can help me 'phone this number' and none of the people helped me. They can't stop phoning you when they want to upgrade your contract after you've said no multiple times... but if there is a problem no one can seem to help you or rectify it, then no one can point you into the right direction.