Telkom Mondo

Telkom Mondo, delivered a wrong order and insisted that was what we agreed on of which it was not true, tried to cancel the contract with them, it was still within the 7 days of cool off period, instead they sent me an address to send back the device to, with no further information of how and who is going to receive the device back and promised that the they'll cancel as soon as the device is received, when they contacted me I was not informed that they where Telkom subcontractors, Telkom refused to assist me and told me that it has nothing to do with them, contract is not canceled yet, please assist me, what are my rights on this