privacy concern

i have recieved money that was send mictakingly on my account, i knew that the person who send the money with call the bank, and what heppenend is fnb bank given that person my personal details without calling/ without my authority. i am really scared that i am not safe on this bank. giving away my details just like that with no communicating with me was uncaller for. i want to take my bussiness else where. my privacy was violated by the company that was surppose to protect me. instead of the bank calling me, to notify me, they give out my details, how sick is that? i hate FNB.this is unforgiveable.