Complaints about my personal loan with Direct axis

I had a loan with Direct axis for more than 4 years and the debt order was coming out of my account every month on the 15th which was R1175... This year in April I paid extra by R1000, so in this December the loan was going to be paid up. The last installment according to their statement was supposed to be R407.88 and I wrote an email to remind them but I didn't get an answer. On the 15th they debt whole installment of R1175 which made my account having a credit of R700. Now I been asking for refund and I am not getting any joy.

I have wrote several emails and called them but I'm not getting any clear response. Someone said I must give them a proof of payment, I didn't understand because they should check the statement of my account and see a credit that is due to me.