Standard Bank
Penalty interest charged not legal!

I'm selling a property bonded with Std Bank.
Despite having submitted written proof of notice at least ninety days before the sale, they are now still charging me penalty interest of thousands of rands!
They can supply NO proof that this is legal! (As per callcentre conversation - recorded by me)
How many people have paid MILLIONS to them without needing to?
It is not even listed or mentioned in the contract?!
HOW IS THIS LEGAL?!
They are BULLIES!
Prove to me that I agreed to the above, and I will pay it without question. Is that too much to ask?!