Poor accounts management

I honestly cannot take the harassment by this company and if anything I will not even renew my contract with Telkom. I am being called and sent threatening email about my account that is in arrears for R 3846.34. I don’t know how many times I have had to correct this and ask them to synchronise their information with Telkom before harassing me like this. Agents or whoever calls and attends to emails doesn’t seem to grasp it. What does one do then?. I need this corrected immediately and for the emails to stop cause my account with Telkom is up to date.