Billing error and no resolution

They made a mistake by deducting twice in December. After I disputed this, they wanted me to pay for their mistake, they added a fee that I did not agree to, and even after I kept rejecting it, they kept saying I owe them, spoke to different agents and they assured me that I no longer owe them. But I just realised that they sent another separate debt order, they took my money so I reversed it and called them to cancel their service because they failed to resolve the issue.