CREDIT INTEL BAD BAD SERVICE

I cancelled my account with Impact Meters in March 2020. There was R178.41 outstanding. Then they billed me again for additional R1000 for a water restrictor.The full amount of R1781.41 was settled on 7 July 2020 and another R600 in August 2020. I received yet another invoice on 7 September 2020 for R284.14. If the account was closed in March 2020 why was I billed in September 2020? I am not willing to pay this. They handed me over to Credit Intel. I have mailed them 9 times and phoned but with no response. My latest invoice is now R1400. It keeps going up every month!