Bad service

It is with great regret that i find myself battling to find the relevant answers from HomeChoice till date. Last year June i ordered set of baby blankets for the amount of R500, i the made a R120 payment end of June month and couldn't pay end of July. By the end of August i made a payment of R300 as my installment was R109, placed another order of a play mat which was R1099 to my surprise the statement came saying im owing R2000. No one from their side can explain why... at this point i paid R100 from beginning of the month and stopped as i noticed my outstanding amount doesn't change i am now owing R2500 when will this stop, how much am i supposed to pay cause clearly my monthly payments doesn't make any difference??? I received a call last month and was promised that they will have a look at the matter and get back to me with an agreement of discount should i pay a min of R150 end of June... i did till now no one called me only an email of Statement telling me to pay R1660 immediately. What is this??? On their advert it say free delivery but massive amount of delivery is cahrged on their statements