debit order dispute

OH WOW!!!!!!!!!!!!!!!!! Telekom decided to debit my account with a whole R5000.00 on the 15th of December I cant reverse the debit order as my bank say It was mandated my myself with Telkom. I do have an overdue account with Telkom I just recently started working so when I call on the 13th or so to find out what my arrears were. no making an arrangement that they must debit my whole salary Telkom cant give me answers how useless. then on top of that my account gets handed over to NuDebt with the whole outstanding balance they cant see the R5000.00 on my account what a Wow Telkom is ****.