Disgruntled customer

I signed up for the cell c router when the fibre was being installed in our premises. Then cell c gave me a good deal that installation in free promised me a black box which I got 2mnths later and was told will not pay for 3 months as I signed up there was a promotion. Now 2 months later cell c says I owe them R3059 when my free WiFi connection has not ended I have been complaining as their consultant told me for 3 months I would not pay. When I send e mails no one phones me to address the issue instead I get an automated response from them. I'm so unhappy about this and now willing to pay as they had promised me free WiFi connection for 3 months it's only 2 and half months and they have disconnected their services but demanding money from me. I would like help so that I do not pay for something I was promised for and now it's not happening instead they demanding money from me