Airbnb and ING Bank Are Pointing Fingers at Each Other Over a $31 Overcharge

I made a reservation through Airbnb and received a receipt for $1,114.59. However, when I checked my ING Bank credit card statement, I saw that $1,145.99 had been charged — a difference of $31.40.
When I brought this up with Airbnb, they told me their charge was $1,114.59, that the issue was not on their end, and that I should contact my bank directly. They mentioned that if I send the receipt to my bank, they should be able to correct it. The problem is that I have been unable to reach ING Bank customer service.
I don't understand how a discrepancy like this can happen in the first place, and I want it resolved. I am requesting that the difference between the receipt amount and the actual charge be refunded to my card.