Deducting money even months after cancellation

I bought a router in October of 2016 from Telkom and it was R199 per month. It was delivered on the 6th of October 2016 and I realised that it wasn't what I was looking for, so I called them to cancel. They came and took the router on the 19th October 2016. However, they kept deducting money from my account, even to this day. Their deductions are not even once a month because this month (November2017) they deducted four times already and the amounts are different. I keep going to the bank for reversals but I'm tired of doing thing because it's costly and time consuming. I went to Telkom so many times and called them but the deductions still continued. Please, I'm tired of being abused by Telkom, I have no money to keep giving them, may they please stop taking my money. Please call me so that we can talk about this properly.