Double billed by lawyers and FNB for the same debt

I took a short-term loan from FNB in the beginning of the year to tide me over. Unfortunately, my financial situation became such that i was unable to pay them back momentarily. In March, I finally got a job and immediately made two payments that were sizable that month. In April without calling me, FNB forwarded the temporary loan account to their attorneys Goenewald and Lubb, who requested I pay the outstanding R1580, I agreed to a once-off debit although it was unnecessary as they could have deducted that amount from my account on payday (they never bothered to call and here whats going on). On the 25th, they made a deduction but it was R1219 and not R1580 as agreed. FNB later that morning also deducted an amount of R1233, not part of the agreement as I should have ben debited only the total outstanding amount of R1580 by the attorneys. I called FNB short-term loans regarding this matter but they have yet to get back to me 48 hours later. To make matters worse, I receive an email from the attorneys informing me that I still owe them money (they are the ones who didn't debit enough money), a balance of R361 that is still in my account for them to debit and end this ordeal!