Harassing me for money I don’t owe

I cancelled my dstv account and paid the outstanding balance of 300 odd now there is another amount of seven hundred for holiday decoder which I phone dstv to query. I did use the holiday decoder for two days and asked the person that assisted in activating the decoder to disconnect it two days later. I phoned in for the voice recording twice and dstv is yet to reply. Now they have this vericredit harassing me about it. I told them I don’t owe them but they are extremely rude putting the phone down in my ear almost every time. Really disgusted