Extremely bad service from standardbank

My husband and I have been customers of standardbank all our lives. All our accounts are with standardbank. We app**** for a building bond which was approved after a lot of fights with the consultants who responded whenever she felt like. Eventually the bond was registered for R ********** . We were told to build to a certain point and ask for progress payment. We did that now that the house is where we need to put a slab. The assessor went out to assess and to our surprise standardbank gave us R4600. How on earth did they calculate that. And when we sent emails to try and understand no one is willing to explain. How did they even get to that 4600.