Settlement Letter

I settled my account paid 170.25 the final amount. Edgars refuses to give me a settlement letter instead they are building a debt for me, saying I owe money like R50 for account insurance and fees interest. How can i have interest on an account with a zero balance. How can you insure zero balance insurance law provides there is no insurable interest with a zero balance. How can you charge me fees? This is not a lease or a service were I have to cancel. It is credit that is settled there is no obligation to say i have zero so please stop charging me. A debt is settled and a settlement letter is issued. Why is edgars doin this now i have to refer matter to the national consumer commission. Emailed an enquiry to accounts email acknowledged receipt but they never came back. I should make a state of the cost i will incur resolvin this matter.