Vodacom provides my customer information to Cell-C

At 11:55am or so, I received a call from 084 145. I answered the call and was immediately placed on hold. Infuriated, I waited until the call centre consultant was ready to speak to me. After a minute or so, the consultant asked me how I was and proceeded to advise me that I had been pre-selected for a Cell C promotion. I was completely outraged and requested where Cell C had obtained my personal information. The call centre consultant stated that they had my information on their database from Vodacom. To the best of my knowledge, I have never granted authorisation to Vodacom to share my customer information. In addition, as Vodacom and Cell C are competitors as defined in the Competition Act, this sharing of information seems to conflict with various provisions of the Competition Act. An explanation and cessation of such behaviour seems in order.