The worst experience I've had is one where I interacted with a provider, I paid my co-pay, they billed my insurance, my insurance paid the remainder, and it see

The worst experience I've had is one where I interacted with a provider, I paid my co-pay, they billed my insurance, my insurance paid the remainder, and it seemed to be done. Roughly a year later, the insurance company audited the bill, determined that the provider coded something wrong, and (somehow) took back their money. So the provider turned around and billed me 18 months later. I called the provider, who had no clue what had happened. The insurance company finally told me that they reversed the charges, and told me I was not responsible for the bill, and the provider had to generate a correct bill. That was the last I heard of it, and I'm still expecting a several thousand dollar bill to show up in the mail..