Pathetic Service

I’ve been signed up on an Telkom ADSL contract for the past 15 months. This is for a 4mbps line(up - to), however I haven’t received this speed even on my best day. The max I’m receiving is 1mbps if I’m lucky. Now surely this is not what I signed up for. I have complained to them numerously and they haven’t been able to resolve my plight, although technicians (SME’s) have come out, had a look suggested a test on my router, which was done and the unit was found to be perfect. I’m still sitting with this problem, please can I get some help.