Vodacom does not want to cancel my contract

Vodacom is giving me a hard time, my cellphone contract ends today, but if I call Vodacom for cancellation, I spoke with an agent by the name of Calib Hariebo, who said I cannot cancel the contract because it was supposed to be cancelled yesterday the 28th of February, and says I can only make cancellation next month, Vodacom wants to keep on deducting my money for nothing, I've finished paying for the device and everything.