Telkom Mobile contract bad service

I cancelled a contract on telkom mobile on the 3rd day, according to the terms and conditions I was supposed to be granted free cancelation and the mobile wifi device taken back, but instead they refuse to take back the device and they sent me an invoice saying that I will be charged for the device that I did not even use for even five days. When I tell the sales people about this they keep referring and referring me to the next person until my airtym is finished.