Cancellation

Am asking for assistance, have been writing to SADV ISP for cancellation of my service as they don't have any reconnecting in khayelitsha, I have already paid then,but they refusing a refund, they refusing cancelling my service with them so that I can join other isp!please any assistance on this poor service, they don't have any call center number to contact only WhatsApp they answer only after hours without help, vumatel once joined them they no longer care about you,they always refer you yo your ISP which is poor not having number to call,it has caused a huge loss and inconvenience in my life.