Cannot resolve their invoicing

Since about September 2015 I have had a problem making payments to Multichoice. I pay using THEIR system on the 4th of every month. The system says I have paid but then I realise that the money has not actually gone through. I regard this as their problem as I have made every effort to use THEIR system to make payment. The fact that it does not go through is not my problem. They have acknowledged that their system has a fault. Last month on about the 18th (January) I went to their walk-in centre in Randburg. I spoke to one of their supervisors. We agreed on how much I owed them and paid the full amount. I tried to pay them on the 4th February but the payment failed. On enquiring about this they told me that I now owed them about R2100. This was 3 times what I thought I owed them. I then received a message from them saying I owed them about R1500. Their system now says I owe them R3035. How is it possible to survive a company like this?