unexplained arrears

My name is Khosi Molo last year I made an arrangement with African bank to reduce my loan installment from R 2264 to half it was done. December i received a statement stating that my arrears are now R13 487.00 and i settled those arrears on the 23 December 2015 in full. January they deducted the half installment and i phoned them telling them that they must take the whole installment cause i don''t want these arrears again and they took the difference same day after a 2 weeks i received an sms from African indicating that they will deduct more i m in arrears by R540 that was in 2016 February 12. I phoned African bank my loan is not in arrears they said they will call me back after 5 working days and they did not. I phoned around the 17 they said it does nt show on their side I also phoned on the 23 Feb 16 no one was able yo explain.29 Feb 2016 my arrears are R1 660.00 from R540. The answer that i recieved is that my account is billed on the 25 th of every month so they consultant was suppose to tell me the will be other charged or she was suppose to add it on the 13 500 that i paid. if i was told i was going to pay that amount upfront on that day cause i had money.must i sufer