Paying for what

We were handed over to Koegelenberg Att from CT International. An arrangement was put in place last year june 2018 for an amount to be deducted every month. I was told by the person that did the debit order arrangement for me over the phone that this is the amount I need to pay every month and there will be no interest. A year later I phoned then to get a shock of my life. I have been paying R 11550.00 for 11months only for the balance to decrease by R3310.00. I phoned in to request a statement I get charged for the phone call I made to them. The interest goes higher even when the balance gets lesser. There is journal interest, interest and collection commission for I don't know what. Thabang informed me that his senior will contact me I am still waiting.