Taking too long to cancel contract

A call centre agent called me around the 2nd week in April offering me a tablet deal. I decided to take up the offer. After 4 weeks I still did not receive my tablet. So after contacting Elite Mobile a few times I decided to cancel in the 3rd week in May. Now when I am trying to take out a contract with Vodacom as a new customer, they say that until Elite Mobile cancels my contract with them I will not be able to take out a new contract with Vodacom.