3 months of hell and destruction of life from Standard bank

I made debit order change request to standard bank in june 2019, i requested they change my vehicle account debit order from standard to FNB, they acknowledged receiving my documents and reassured me all was in order. To my surprise they mixed up my home loan account with my vehicle account. They debited my home loan account from FNB instead of Standard bank, and kept debiting my vehicle from standard bank. I called them they apologized and promised to fix the mistake and reverse the money back to fnb. They messed up my debit orders. Now in august nothing has changed, they repeated the same mistake and they are refusing to reverse the money they took. Now they debited my vehicle account again from the wrong account and they are giving me the run around. This is the 3rd month in a row doing this and they always tell me its sorted its sorted. The fnb account belongs to someone else and they took money without his permission. All my debit orders are bouncing and my credit record is on the line. I spoke to a lady called Lauren Adams and her line manager who were not helpful. its been 3 months of hell with standard bank vehicle finance and home loans. Please help