Billing even after cancellation. Rain is a ****

Rain wifii is a ****. The connectivity was very poor and they did not have a fibre. I had to cancel it. But they kept on billing me. I have been cancelling it, but they kept on billing me even though I was no longer using their wifii and I had a ref no that I cancelled it, and the bill was increasing every month because I had to block my card to avoid the bill from them.