No clarity for cancellation policy of contract within 7 days-30 days notice period

Assistance in cancelling a WiFi router contract after 3 days without even using any data. Currently at Maponya mall my dad took out a contract with your network for 200GB per month for around R800, shortly upon coming home we saw a much better deal from Neotel at R700 for uncapped data. We decided to return the router on the 3rd day having not touched the router at all. And understand there could still remain some cancellation fees but the store is now holding us ransom and forcing us to take this deal even when we have explained that we are within the 7 days return to store product/ let alone the 30 days in which we can return the product in. As I speak we left the router at the store and used no data at all from it. They are talking about commitment fees which we do not agree with. Please assist us in this regard. Our contact person at the store has been a lady by the name of Gugu. I write this on behalf of my father because he is visually impaired. He is beginning to feel that no proper explanation was given to him before signing up fro this contract and he is now being taken advantage of. Very sad to see this from Cell C.