Canceled Contract Handed Over

I am extremely frustrated and stressed. On the 17th of February, I successfully cancelled my cellphone contract with Telkom aftrrrr having settled the outstanding amount, yet I am still being billed. To make matters worse, the account has now been handed over, and I am being harassed daily with emails and SMSes threatening legal action against me. Despite numerous attempts to resolve this, I’ve just received yet another bill for this month. This is completely unacceptable. I need this resolved immediately.