Standard Bank home loan paid R700000 on R300000 loan still owe 18years, no clarity

I am extremely disappointed and frustrated with standard bank home loans.we took a home loan in 2013 for R300000 .To date we have paid over R700000 or more than what we borrowed. We were shocked to learn we still have 18years left to pay. We have gone to the branch and called multiple times to ask for a clear breakdown and explanation. Each time we are taken from pillar to post with no straight answer. No one can explain how much interest, how much to capital, what our interest rate is and why after 12 years of paying, our balance is still so high