Cancellation of contract

They phoned me and they came here and tell that i must buy shares and i will make 40% profit so i signed the contract and they never tell me that there is a cool down period of 7 days. So after 2 weeks i want to cancel the contract and they don't want me to cancel the contract because i thought by myself there can't be a program with such a high price R33,500 So the technician came and install his program on my computer and i click that there is no serial number then my mined tell me this is a free program that they install on every bodies computer. You see i now programs when it is a free program like (Mozilla Firefox, Paint net, Google Chrome, Malware bites, Team viewer, Acrobat reader, DVD Shrink) and i check on the memory stick they got most of this programs by the extras, Now the first debit order went off and i reversed it. Can you help please? I want to give them over to the scorpions.