Bad service/ ****mers

Afternoon

Purchased a decoder with the OnAir company. Was on a 24 month contract. Now have issues with them. They don't respond to me and keep debiting me after the contract. I they debited me for an insurance which I did not agree or sign for. When the bank to block the debit order they some way still manage to debit me. Need assistance. Thinking of closing my bank account to a different bank