Incorrect payment amount and enormous interest

We have been making monthly payments higher then what installment amount is supposed to be since 2012, but balance keep on growing high and high. We suppose to have been done with full balance in 2014 but still huge outstanding balances, we wanted to give goods back already but the Sales people at Lewis Stores in Mitchells Plain told us even if we return the goods they will take it back but we still have to pay full balance which I feel is wrongly calculated. I have been told by the Sales Team at Lewis Stores in Mitchells Plain said this is a new law when you pay but interest accumulates daily, I need help and assistance ASAP as this problem is effecting my health whereby I am stressing and my blood pressure is affected.<br> Can someone please get back to me.<br> <br> Kind regards<br> Nazeema Petersen