Standard Bank finance charge

I am currently under debt review, I have been making payments to my standard bank credit card since November 2018, and my balance hasn't even dropped a bit. They keep charging me a finance charge, which is quite a big amount, so the installment i pay every month does nothing to reduce the balance I owe. What is this finance charge, I haven't used this credit card in years, I am just making payments every month in the hopes that i can reduce the amount owed.