Why have Altech passed on my contact information

I have 5 business and 4 personal contracts with Altech Autopage. They have passed on all my contact details to a marketing company called EC3 who not continuously harass me and my family regarding upgrades. I never agreed to them passing on this information and cannot get the EC3 consultants to stop calling me - sometimes 2 to 3 times per week. I have called the Altech Customer Care who say 'we don't know who these people are.' I believe Altech are in breach of the POPI act