Inappropriate Behavior & Bad Customer Service

I had a very bad experience with Standard bank home loan for six months. I cannot believe that such a big bank can fail its clients for something as simple as transferring money paid erroneously into my one Home Loan to my other Home Loan. I wonder how bad can it be if the money was paid erroneously into other clients account. They failed to assist me in numerous occasions instead I have been send to three different departments, referred to two law firms, one close off the matter on their side without informing me, I'm being charges high interest rates while I paid more than what they dispute, but they cannot help in transferring the funds in a correct account as requested numerous time. Please assist, I have every name of the agent, dates of call, proof of payment, email correspondence. The bank want to sell my property despite their incompetence.