insurance cover cancellation

when I cancelled the insurance on the 13th of August 2025 I received a SMS confirming that I have indeed cancelled my insurance contract, I was billed the same month for the insurance monthly charge, I paid it, now I have been billed the second time in September 2025 and I am being threatened to pay or else they will disconnect my other contract Worst service ever,I have logged a call and call the customer centre but still no assistance