6 month cancellation fee

I signed up to Afrihost RAIN internet service because the fibre installation was taking too long (they promised 6 weeks and one year later still no fibre). I paid for 6 invoices, and then cancelled under their 6 months free cancellation rule and they STILL charged me R999 to cancel, because in their view, I submitted the cancellation IN month 6 instead of in month 7. That is complete nonesense! I am now in arrears with them owing the R999 - surely this is not a fair penalty under the Consumer Protection Act? What is worse is whenever I submit an email they just give the same repetitive response - basically not addressing my complaint.