Standard Bank Home Loans - Appalled by Service

I have qualified for my Homeloan in August 2003. I started paying in September 2004. I got a rate of prime minus 2%. After I have send through this account to Charted Accountants my bond is supposed to be settled as I paid most months in advance with certain amount - some months even double. Now that I have almost paid 3 times my original bond amount back after 17 years, Standard Bank still insist that I owe them R440 000.00. Something is seriously wrong and absolutely nobody wants to assist you, including attorney offices as they are basically all on Standard Bank Boards and dont want to offend the banks and loose any form of potential business so rather turn the eye in another direction. I give Standard Bank up to 16 September 2020, 13:00 to make urgent contact with me so that re-calculation can be done and the correct amounts be allocated. It is a shame that we as paying customers have to go to these extents to get somebody to attend our matters. I am not very pleased at the moment. How can I pay on a bond of R740 000.00 with an interest rate of prime minus 2% an amount of over R1 980 000.00 and still owe the bank over R440 000.00. Please provide me with the formula that you calculate this with, or are you rounding of amounts and interest rates, which is also not the legal way of doing business. I have also paid since day one an amount of almost R1000.00 on Home Owners insurance and two claims have been granted - the rest is always not covered. I need urgent answers. My next stop is the Umbudsman.