Cancelation of contract not actioned

I am writing this review with a heavy heart between march and April this year I have cancelled my contract after I received the phone that we were not agreed upon, the phone was returned and collected by courier company. I was told the the contract is cancelled, yet todate I am still receiving sms's that my account is on arrears. This is really upset me because I have had several engagement with the company via telephone and WhatsApp channels but still nothing is happening. I demand this contract to be cancelled and send me confirmation cancelation. And please stop sending sms's they depress me. Below is the last sms I received:

MS Phala, get access to grocery discounts of up to R1500 redeemable at Shoprite/Checkers/Dis-Chem. Pay Urgently your Blue Label Telecoms acc arrears R658.00 @ ABSA, Acc ***, *** or visit https://bit.ly/336Gji4. Call ***