Sharing of personal information without consent

I have a 3 contracts with Vodacom which is currently up for either renewal or upgrade. Recently I have received calls from a call centre (not operated by Vodacom) regarding these contracts. When I signed these contracts with Vodacom I explicitly stated that I do not want my information to be divulged to other parties, yet here I am receiving calls from a 3rd party. I believe that this is in breach of the Protection of Personal Information Act.