Vox deduct money without consent

I have recently signed up with Vox for my fibre at home. After signing up and getting all the installation done, I discovered that they automatically, without my consent, deducted my money from my bank account as a debit order. I have tried endlessly to contact them and get this resolved, but the accounts department does not answer and customer care keeps telling me that they will get accounts department to call me and sort it out. I am furious about this, as it has taken me so much time out of my day to try and sort this out, but all I get from them is empty promises. How is this even legal that they can just deduct money from my account????