billed for 2 years

I'm not sure that there is much that can be done about two years of overcharges. There's a presumption that the customer will take some action to correct such errors in a reasonably prompt manner. Having said that, I always recommend when money is a issue, the customer limit phone calls, e-mails and social media contacts to one or two attempts, because these methods do not preserve your legal rights. You should fairly quickly switch to writing business letters conforming to the requirements of the Fair Credit Billing Act and deal with the issue only in this format. If it come to arbitration or small claims court, you want to make sure you have a paper trail on your side.