Bad customer services

I am a Game store customer and i could not believe my ears upon finding that an account that i paid the outstanding amount has been added interest ,service fees and insurance to a balance of Ro. I paid the outstanding balance on the 3 September 2020 and by the 11 September 2020 , i owe R71.20 AGAIN. I called the call center and i was given a very weak explanation . Apparently the account is interest bearing from the 10 of one month till the 10 of the next month. So i said how was interest charged to a Ro principle amount then i realise the system is programmed in such a way whether your outstanding balance is R0 or R1OOOO it will still add insurance , interest and service fees for the period unless somebody intervene and remove the charges . This is very disappointing and also frustrating towards having peace of mind that your account is indeed fully paid off. The lady was explaining about agreement where rules are attached and quite frankly that account was opened and i was told alot of stuff but no copy of agreement was sent to me , where i could see and further understand the GAME credit financing principles. So the lady at the call center said i will be given an settlement amount and i asked how do you calculate an settlement amount where the outstanding balance was paid and i saw my balance was R0. So my question is do we over pay on this accounts as it stands or is just a way of making us the customers pay more . I am awaiting the next account and it will be very strange how i will have to pay interest, service fees and insurance just because i had an account with GAME.