Bridge of Contract / Overpricing

I signed up for an MWEB Premium Uncapped ADSL Contract on the 20th August 2013. The contract is a 4Mbps line speed. Only to find out that Telkom can only handle 2Mbps on their lines. Since I am running a business I was concerned and started cornering MWEB Support because of slow internet that is caused by size of the line speed. This has affected my business a lot and I have been paying a contract worth R899 consistently every monthly. As soon as I queried after my discovery from Telkom exchange I was advised by MWEB Technical Support Assistant to migrate from 4Mbps to 2Mbps without even acknowledging that they sold me a non existent contract worth R899 whereas I was suppose to be paying R509.00.I have been overpaying for over 14 months, and every time I contact MWEB for Credit Discussion I am sent from Pillar to post and they have already billed me for the new contract without assuring me about a refund. I want MWEB to compensate my business for ruthless services and not solving y problems as a service provider.