Terrible service by Woolworths

I am not happy with the service received from woolworths regarding my store account. I was owing them and they listed me on ITC. Made arrangement with their collections company Dmc and paid them in full. Was retrenched which led to me not able to paying my account however when I was employed I made arrangements to pay my debts in full. Got a paid up letter from Dmc and was advised by one of their consultants that I need to send it to woolworths in order for them to remove me from the listing. It's been more than 6 months now contacting woolworths and advising them that I paid and emailed the paid up letter however I am still listed and they ruining my credit records as I am unable to apply for any credit. The most annoying part is that the consultants working there are so in competence they don't know what they doing.