Still getting accounts for no service

We app**** for Wi-Fi in November of 2014. Since then we have had countless technicians coming to fix the problem and I have swopped the modem about 10 x. In the last 6 months the wifi worked about 3 weeks. In all that time I have been paying my account for no service. I closed my account more than a month ago because I refuse to pay for no service anymore. Telkom is still sending me invoices! Their website is not user-friendly and you can't even lodge a complaint there. Going into their store is a nightmare!<br>