Double billed

A few months ago I upgraded to a 10mb line, 50gb data with DSTV explora. Since then, I have been billed for a 20gb data bundle as well as a 50gb data bundle. The 50gb bundle isn't even linked to my account, so I get capped at 20gb even though I am paying for both. I managed to get through to the call centre once, however they could not help me and transferred me to someone who never answered the phone. I have tried again many times to get through, but I can't listen to the hold music for another second.