City Tax Credits

For the years of 2016, 2017, and 2018, I lived in Akron, OH but I worked in Wooster, OH for the USPS and they did not take out Wooster city tax. I always paid Akron city taxes because the tax rate was higher and I was told I would get Wooster city tax credits. I received a letter in the mail with no warning, stating that I owe back taxes from 2016 and 2017 for Wooster. Would this be a mistake on Wooster's part? Unfortunately, today is Saturday and neither of the tax offices are open, so I can't call them. I hope the question makes sense.