MTN is *****ing my money

I am still awaiting for MTN to stop debiting me. On the 2nd March 2020 I made a a two month advance payment on my cellphone contract. Despite this, debit orders went off at the end of March and again in April. When I called in and e-mailed numerous times, I was told by your Credit Management department that my case is with the Banking department. To date this is still the story. I need these debit orders to please stop now.