I got a wireless Wi-Fi router ,i unfortunately realized there's no telkom coverage in my area

I got a wireless Wi-Fi router ,i unfortunately realized there's no telkom coverage in my area. In a week's time I called back and told them my situation and was advised to return that device as it didn't work at all. Courier guys came and took it back.. A month later I'm being billed,twice and being called my NuDebt debt collectors..I then settled that apparent 2months bill and advised to call 081180(it says number does not exist!) Now I don't have router*never used it* how ever I'm being billed monthly and can't cancel