Extremely unhappy with wifi network and still pay

We experience highly bad network on our vodacom wifi. We reported it on 4th October. And mailed last week again. No success. Went in on Friday, Saturday and Sunday. No luck. Today after 21days of reporting the problem and still not fixed we called to cancel. Only to get a shock of our lives. Have to pay R7000 to cancel contract. So we need to continue paying against a high rate for wifi that is extremely poor. This is not fair.