I'm livid with MONDO/MTNSA

I am livid with MTN and MONDO . I had agreed on a contract in May 2020, upon receiving the sim-card. I called MONDO to have the contract cancelled. I spoke to Nikita, Nothemba, Thami, Miacan sp, Nombuyiswa, Nodoli, Tyrene, Winnie and today Lerato. All I am asking for is for them to stop debiting my account. I never used their sim card it is still in tact, Why should I be abused by these people?