Incorrect billing & Woolworths don't have answers

I was offered a loan for R13000, monthly installment +/-R420.00 when my July 2019 first statement displayed an installment of R2900. When enquired I was enlightened that the Balance +/-R420 instalment, +/-R1200 initiation fee together with interest is +/-R1700 and the difference between the R2900 and R1700 is the excess amount due to entire loan amount being paid out. However this is a new loan,this is the first month and it is the first instalment, there can be no excess amount or arrears on the account, highly impossible. Woolworths goes around ripping people off.