If you had told my great great grandparents that in 2017 people would pay for jeans that were intentionally dirty, they would probably think we were doing okay.
Something similar to that happened to me about a year ago. I was at a clinic and they told me I don't need to pay for that day's visit and that they actually over charged me through the years. I will have a $50+ credit. 3 or 4 months later, i went back to the same clinic and they told me there were some insurance deductible confusion and that there is a mistake on my account. I actually owe them about $130+.