deducting money

I purchase a sim from them about a month ago, received my sim but when i tried to use the sim it was never activated, tried to phone them and email but they just kept on ignoring me, and today they deducted money from my account and I never agreed, The first time I paid them it was with a EFT (how did they get my banking details?) I am so tired of people taking advantage of the pandemic to ignore customers and just take money as they want.