Billing

I am not happy with supersonic fibre,first of all when I signed up ,They told me it is not a contract and if I miss a payment then they will switch it off for the month Which I have not paid, but I was not around for 3months and I expected them to block my services the 1st month I missed a payment. To my surprise the router has been working for 3 months,my account was overdue with 4months.I paid for march in July when I returned.to my surprise when I login to their portal I still have 3 outstanding invoices. For april,.May and June. On the 26th of August I decided to pay for all the invoices, today they send me an invoice stating that I have to pay R399 due on the 7th of September. My services were disconnected the whole of August but they want me to pay 399 from what I know I am supposed to pay R399 end of September because I was reconnected on the 26th of August so I will only start paying for September month end.they can't charge me 399 for 5 days of August ,that's ridiculous