If this was truly a violation fine issued to Avis by the tolling authority, then I think that you must first clear things up with the tolling authority, and then get Plate Pass to reverse the charge. If, on the other hand, this is simply a Plate Pass charge for the toll and their fees, then you must submit documentation to Plate Pass that the toll in question was properly charged to your personal E-Z Pass account.

Did the rental vehicle have its own windshield-mounted E-Z Pass transponder encased in a metal box? If so, was the metal box completely closed when you incurred the toll?