Had a recent Avis rental, pickup at BOS, drop-off downtown Brooklyn NY. We paid cash at all toll booths we passed through and didn't at any point touch / use / interfere with the EZPass device. Avis have now billed my credit card for a toll plus a 19USD "convenience fee". They have absolutely refused to refund this and are stating my dispute is with "the issuing authority" (including for the 19USD fee). I'm fairly angry that this has been charged (on a rental costing almost 900 GBP) - any suggestions about having the charge removed?! Is this a common tactic from Avis?

Edit to add: I'm a British citizen, live in the UK but was visiting US on holiday; car hired via Avis-BA website, paid with UK issued credit card