First National Bank
Unauthorized debits from personal accounts

I had a credit card with fnb almost 7 years ago, which i filed to pay due to unemployment and retrenchement. For the past years no one had contacted me therefore card was written off. And considered "prescribed debt", I just started banking with FNB for almost 1yr and half now, and all of sudden they debit money from account, without a letter, email or phone call.
This means they FNB is able to go into my account and view my personal transactions, i find that apaulling.
When i call to query this i can never get through to legal.
My banking account is personal belongings and only I can authorize debits.
So who can assist me now or do i have to just change my banker and move on.