Interest rate increase without my consent

I app**** for a home loan from different banks and chose the cheapest which was Standard bank, at point of registration I get a completely different rate which is way higher than its competitors. My contract has incorrect salary details etc . My developer threatened legal action for delaying to sign so i raised a query and signed. Now i am told by a lady from standard bank that they cant do anything, CANT!!!!! i ask for a re-assessment i am told sorry registration has gone through already. I still do not understand why my credit record is better, my salary better but the lady from standard bank tells me my interest rate is higher. Moving forward????