Originally Posted by
lovesfashion
Right, that's what I did
"added the rental plate to the sunpass account immediately."
I'd be calling SunPass to query/complain about it, not PlatePass.
PlatePass is charging you because SunPass charged them, which based on what you've said should not have happened - all charges should have gone straight onto your account and nowhere near PlatePass. The fault here almost certainly lies with SunPass.
That's not to say that PlatePass won't simply reverse the charge on the grounds that it's easier than fighting it, but SunPass is who your real beef is with.