Bad service

Chatz connect Address: Glasfit Building, N12 Main Reef Rd, Klerksdorp, 2572 Phone: ********** We bought a Hauwei wifi modem in Jan 2019 on contract at the above shop. When we tried to use the item, we were told that the modem does not work without 4G, which was not available in our area. We immediately contacted the shop. They said we could return the item, and they would send through a cancellation. We handed in the item within 30 days to the shop. We are still paying the monthly premium without any service. The cancellation is not done and the shop keeps the item. We phone the shop constantly with no feedback. They keep on saying they will phone back or transfer the contract etc. but nothing happens.