Unreliable information and quick to black list

I have been a reliable and good customer for Edcon group for so many years and my account was always up to date until late last year when i experience financial problems, I used my air time to call ed-gars and inform them and request to make and arrangement with them to pay R300 instead of my monthly R600 installment. To my surprise Three month later my account was handed over to attorneys . I don't understand why the encourage us to call them and make arrangements where as they know that they wont stick to that arrangement, When i call them every time i get a different person who promised to investigate and come back to me but they never did. How can they black list me cause i have kept my promise of payment. Edcon doesn't care about about its customers.