Standard bank home loan *******

We have had the most awful experience with this bank in regard to the home loan my mother took out in 2016. The home loan was for R350 000 to be paid off in 8 years as the old lady had an initial deposit of R500 000. Firstly, the home loan was registered for 20 years and not the 8 years initially agreed upon. A couple of months ago we called the bank requesting a settlement amount as the home was going to be put up for sale as they require a 90-day notice period. The house has since received an offer and we have been to that Standard bank will be taking R324 000 from the proceeds of the sale however last week when we requested a statement it R320 000 which is "understandable" as this amount is calculated for the remaining years on the bond. Where is the settlement amount as they will be getting their money way before the initial agreement? Stay the hell away from getting a home loan from them, rather get Finance from another institution such as Nedbank or SA home loans (Capitec)