Money deducted without my consent or knowledge

On Monday 2 March 2015 I paid R150.00 to the lawyers of FNB for an overdraft due and I also made arrangements with them the previous week to pay them R300.00 per month. On Thursday evening I saw that R900.00 was deducted from my FNB bank account. I went to FNB Brooklyn branch to inquire about the R900.00 taken after I made arrangements with them to deduct R300.00 monthly. The FNB consultant said that the lawyers have the right to take the money out of my account and I should be grateful that the whole amount due to the lawyers was not taken out of my account all at once. I was not informed that R900.00 was going to be taken from my account. FNB says the transaction will not be reversed. <br> I am very unhappy because I am going to struggle hard this month. From my side, I went to make a payment and made arrangements to pay R300.00 per month. <br> So why was R900-00 taken all at once out of my account without notifying me? I urgently need assistance with this matter please.