PowerFlex Cancelation request

This company finds a way to take money out of our pockets. In April I asked my mom to cancel the contract she took for me in 2021 because they kept on encouraging her to upgrade whereas that is not what I wanted, until I told her to cancel it so my number can be prepaid again. 2 months back I subscribed to PowerFlex and last month they did not use the method of payment that I chose, I take it they billed my mother again... Today I called to cancel the subscription they say it doesn't allow me to although one of the points on the app when I subscribed said I can cancel at anytime (it's still there), their reason says I must first convert the number to contract for the plan to be cancelled, and contract with them through my mom's account is what I don't want cos they keep on robbing her.