Personal loan unauthorized double debit order

im extremely upset and disappointed with the services of Nedbank in regards to my personal loan, Nedbank personal loans allows an individaul a six month period for arrangements as i have been told by the consultants. i had a three month arrangement (Sept - Nov 2015) with nedbank since it has been a tough financial period. In the beginning of December i received a call from nedbank asking if im able to make the full payment in Dec, i did inform them that it is a tough month since i was not due to receive bonus so another arrangement was placed for dec 2015 for which i received a sms confirming the arrangement, on the 15 Dec i received my salary early due to holiday period , nedbank debited my acc with the full amount of R1775 and taken off a second debit R1775 totalling to R3550 an arrangement was for R1065, R2485 was supposed to be refund when i had reqsted for a refund of that amount i was asked to make an arrangment for the arrears amount which i have done -15/12/2015 my refund was declined. after calling numerous times theres has been no joy, i called back thurs and no approval passed on my 2nd req, no joy to speak to a manager, unauthorized debit.