Am I being petty ?

[u/Itshouldbeeasier9585]

My husband and I own a small business and have used the same fleet salesman at the same dealership for over 10 years. In January 2025 we signed the lease on my new personal vehicle. Same lender we always use, autopay setup immediately as usual. Yesterday we get a call from the collections department of our lender, we have over $200 in late payments plus $80 in late fees. After some back and forth with the lender and calling our sales guy, turns out the finance guy didn’t input the correct sales tax. Apparently sales tax changed Jan 1st of 2025, we signed Jan 9th 2025. The discrepancy in sales tax made our payment about $15 more than the lease agreement we signed. I always opt for paperless billing and we have had no clue about the monthly $15 underpayment, until the phone call yesterday. I’m refusing to pay the late payments and late fees. It’s purely principle for me at this point and I believe the dealership should cover it, plus cut me a check covering the discrepancy for the remainder of the lease. Am I being unreasonable?

[u/ryangilliss]

I'm guessing you set up your autopay for a fixed amount as opposed to the total due for the period