Installment not decreasing

I have problem with home choice they are over charging me and my money is not decreasing am always over due with home choice I bought 2 iron R400 and the other is R700 for 3months, they say all cost are R1357. I payed my first installment of R350 at May , and I order blankets 2× combo of R1999 each for 3months payment and again they said am owing R5000 and I did my first installment on 6 June for blankets of R1600 +R350 for my Irons and on the 11 June last week Friday I payed R3100 and the money is not showing decreasing cos the are sending me massages that I have an outstanding of R1660 I can't pay for something that I don't know homechoice is robbing us