Cancellation of debit order

I bought furniture at russel Amanzimtoti , my sales adviser was super excellent ,Problem is with the head office or whoever who is in charge of payments ,we made agreement of debit order to be on the last day of the month , only to find out that they do debit whenever they want to ,now I cant use my bank statement due to their unsuccessful payments ,that they do before my payday , I ask H them nicely to cancel my my debit order ,since they send massages or call me before my payday accusing me of not doing payment in time ,they refused to cancel my debit order ,because i wanted to do payment strait to the shop ,I have never had bad service like this in my life ,one of the guys who called me hang the phone while i was talking ,Iwas asked to email bank statement , i went to the bank ,they gave me 12 pages bank statement ,which is R13 a page plus the bank charges of their unsucessful transactions , Why are they treating me like this ,I am very upset , Do I have to spend my money because of your bad service , I hate the day I made a deal with Russels