unwanted 24 contract linked to special offer

I got a phone call from multichoice to say they were giving me R30 off my premium. I have no recall of them saying that this would become a 24 month contract. This is a contract that I have taken for an elderly man in assisted living who has dementia. There is no way I would have agreed to a 24 month contract. Now I have had to pay R180 to cancel it