Pathetic service and interest rates.

We closed our account with Telkom and paid 5 cents too little. After about 6 months we received letters from lawyers that we owe over R350 due to interest on 5 cents. Then we paid the amount and we are still receiving letters from lawyers. How can we as public get Telkom to reimburse us for our time and phone calls because they didn't let lawyers know the account was paid. They are quick to threaten us but slow to sort out their problems.