Billed top dollar for substandard service

We moved to new business premises in Waterfall as of the 01st of May. We app**** for a Telkom line and adsl line. Since installation date we have had a problem with the internet line dropping. We battle to download emails, do internet banking etc We have logged faults which haven't helped. After logging a second fault we are then told by the technician that the exchange in the area cannot handle the load due to the development of the area and that what we have is basically the equivalent of dial up - slower than 3g. Our billing however is for the high speed adsl line we ordered. My argument is the new mall didn't spring up over night surely Telkom could have upgraded the exchange with the obvious upgrade that is happening in the area. Now they tell us that they are busy with the upgrade and we can only expect our line to improve in October - do I now get a discount from May when I had my line installed until October when they are then fully able to supply the service they advertise? I don't feel it is fair to pay top dollar for a substandard service.