BlueTech not cancelling contract

In December I signed an LTE contract with Telkom through Blue Tech Retail. After numerous false starts, courier errors, sim card not being activated etc. I cancelled the contract within the 14 day period afforded me under the CPA. Telkom has billed me for the service every month since then and Blue Tech has done nothing to fix this. Emails go unanswered - both addressed to individuals and through their website email portal. Telkom says they can do nothing as the contract is with Blue Tech.