Telkom No Service

Ever since I got my adsl line at home its been problems. Telkom Walmer Park, where i got the contract for my adsl, assured me that I would be able to download abything at atleast 4mb/s. At this stage it got so bad that I'm struggling to get 300kb/s. I reported the problem a couple of times and still no feedback from them. I'm at the point of refusing to pay them anymore because its more of a hastle to have it then it is a privilege. Please what am I to do?