Cancellation of Contract

I have been on a cell c data contract since March 2019 and was told that my contract will expire on 28/02/2021 and i will need to upgrade. I have changed my network and taken a new contract with a different service provider in February 2021 since i hardly get coverage with cell c and know that my contract is about to end. I was under the impression that my Cell c sim will go back to prepaid in the new month however i received a call on the 3rd of march 2021 saying that i am due for an upgrade and if i dont upgrade i wont be charged at the discount fee of R149 for 10gigs which i had on my sim. I was told that i will be charged a new rate if i dont upgrade. I went to the cellc branch on 4th March to query and was told that my sim does not automatically go to prepaid and i would need to call to cancel my contract. I called the retention department on 5th march 2021 and was told that my contract only expires end of May and i need to call in April to cancel. I contacted cell c again today and i was told i can only cancel on 30th April 2021. I would like to cancel my contract because i dont have a need for this contract anymore since i have taken up another contract with another network. Each time i call the retention department they try to stall the cancellation. I need my contract to be cancelled and i dont mind paying the additional fees.