Vodacom selling personal data??

I am being harassed by a company \authorized by Vodacom"to buy value added service from them. I have instructed them numerous times to stop calling but they persist - sometime 2 - 3 time a day. They got my personal information from Vodacom - how can Vodacom do that?? <br> <br> Vodacom - please call me so I can cancel my contract.."""