Poor customer service

When I took the policy was never given any contract . They only sent the welcome pack when 3 days after I sent cancellation letter. I then received an invoice for early cancellation which I was never told about. When ever I send them communication to enquirer about this, I never recieve any response except for auto reply with a reference number and it ends there. I have now learnt that the bill has now doubled in value and I have been handed over to debt collectors. I won’t take this lying down because it’s their fault. I when I call , I’m sent from pillar to post. They should just close shop because they don’t seem to know what they are doing.