I am disgusted

So recently a paid up my edgars account, however, had forgotten that I had my cellphone insurance, so after 2 or 3 months I get a letter in the post to say I have not paid my account so I call into the call centre only but to argue with the agent as she is telling me I spent on my account for an amount of around R300 odd and I tried explaining that I had not I had paid up my account.after a few minutes she realised it was my cellphone insurance of R109 ( keeping in mind that when I took out my insurance not even a year ago it was R89 so I'm not too sure how she got to R109 nevertheless ) I said I will pay the instalment every month of R114.52 according to the agent witch I did however I still get statements saying I still owe the original amount of R300 odd so I'm not too sure if edgars is trying to make a buck or two where they can or if their agents cant calculate but I am extremely disgusted. I have emailed twice and all they seem to reply is to ask for my I'd number witch I then provide and still no response. I also argued with the agent about the fact that in my contract ito says if no payment cell phone insurance will automatically cancel witch it clearly doesnt!!!