Disgusting service from WebAfrica

I had a contract with WebAfrica at my old address, cancelled it because I was moving, I still used Web Africa at my new address so took the same router with me to the new address. They sent me an invoice for R2000, telling me I owe for the router, as they now say I have 2 routers. I have been on WhatsApp where they agreed to credit me and then declined because they say I have 2 routers. They are also overcharged me on my new service. How we hold them accountable for what they are doing. So fed up