Telkom contract finished paying but they still debiting

I had contract with Telkom which was taken in the year 2020/2021 for Samsung S21,then i lost a phone which i claimed insurance to pay out the outstanding amount and called their billing department to settle and close the account , they provided me reference number and settlement amount to pay out which i settled and from there i opened a new contract which is currently active and paying well, month end of August 2023 i was shocked to be debited twice the current one and for old phone which i settled , i then reversed the other debited order which i didn't know about and they again on the 15th they debited again 1250 which i reversed because i was also not aware of it and i have never authorise it. so i logged a call to explaining they referred me to telkom store which they assured me that my previous accounts where closed now , now i am being harassed by nu debt which is the company collecting for telkom threatening me with summons for amounts which i disputed with telkom