Cancellation of device

In November 2020 I cancelled the device with the cell number ***. Since then, I am MONTHLY billed with the amount of R171.00. On 19 February 2021 I spoke to Phumeza at the Cancelation and Upgrade Departement. Reference number ***. I requested again the cancelation of that cell number, and also that I should be credited for the payment done since November. Nothing happened. On 11 March 2021 I spoke to Zelma at the Cancelation and Upgrade Departement . Ref nr ***. She also promised to cancell the device. At laaste this time I received a SMS indicating that the contract will be cancelled by the end of March 2021. BUT I Again received a bill for R171 at the beginning of April. I am so much despondent, unhappy and upset with the poor customer service of Vodacom. I demand a refund with emmediate effect.