FNB performed ********** activities on my account

I have a cheque account and fnb refund to offer me overdraft facilities. I had planned to move permanently to this bank but I have noticed that there are stranger transaction taking place in my account. Because there was no funds in my accounts but in my savings. They made payment of R56 rands for toll gates and charged me two R150 for paying from the overdraft facility. This was not our agreement that R56 will have an interest on R150 within 7 days. Meaning I paid R206 for R56. This is ********** activity.