billed for service i never had

Telkom mobile sold me a LTE service over the phone.<br> <br> i told them that i don't have LTE reception, yet they told me according to the coverage map i do.<br> <br> so i accepted the service.<br> <br> once i received the modem i tested it and did not have LTE coverage.<br> <br> I cancelled the contract immediately because i did not get what they sold to me.<br> <br> now i'm billed R4699.33 for cancellation for something that i never had.<br> <br> they can not bill me for something that is their fault.