Unauthorized deductions from account

I opened a Silver Cheque/Credit card from FNB in 2008. In 2009 I was sadly retrenched and a notified all my creditors. I also had voluntarily insurance on my accounts at FNB. These attorneys phoned me and I informed them and requested I want a signed copy of my contract which they stated they will request from the bank. June 2017 they just started deducting money from my account. First it was just over 300, then R447 now September they took R2881. Every time I complain and they cannot give me any legal documentation that gives them the right to deduct this money from my account. The Attorneys state it is the Bank and the Bank said it is the Attorneys. I need my money back as I have given proof that I paid for insurance but they just ignore my request. I feel why should I make arrangements with them to make monthly payments if I had insurance. They should inform that to the Bank.