Extremely Unprofessional Service

I have a 24 months Laptop contract with Telkom, which is due to expire in April. I was on a debit order with them and i was paying every month. Until they debited on the wrong date and i had no funds in my account. i was not aware of this and after 3 months they called to notify me, and i paid the outstanding amounts. which i was told was up to date. so when i asked how they would recover the rest of the money as my contract was up to April they advised someone would call me to advice. till this day no one called me, and when i wanted to apply for a contract phone i found out i had been listed. not once did i get a call from them to notify me of this termination fee that i had to pay, they just handed me over to ITC, Now i am unable to get anything on credit. I went to the store on Sat the 24th Oct and made arrangements to pay the amount at the end of the month. Now they have gone and debited my account without my permission and i have a bounced debit as i do not have enough funds and i was not aware that they would debit as this was not as per our arrangements. As you are all aware it is extremely hard to get hold of Telkom and you will hold for hours on end with no response.