Contract Cancellation

Good Morning Please assist i take the contract with Vodacom and the following day i return back the device but they refuse to take it back and they told me to call call center and i did and call center told me to return the device back so that they can cancel my contract still the manager refuse and i was told that they deal with sales and the franchise. i been trying to call Vodacom to assist regarding this matter even now, it's been a month i have not yet receive feedback and also my network is bad since i change from prepaid to contract.