I did a quick check on their website (
http://www.rentatoll.com/), and the company is one of a growing number of companies that provide "rental" transponders when you are in a rental car.
Now, if it was on your rental, you should see other toll charges on your rental receipt as well as the rental fee for the device.
If you did legitimately, if unknowingly, rent this device, then the violation could be from a time when you went through a tolling facility and it failed to register the device.
If you did not rent such a device, then you may be the victim of a clerical mixup where the violation got tagged to you instead of the actual renter of the device. If they or OOCEA could provide an image, you should be able to clear this up. In this case, IMHO, I don't think that it's a scam but rather incompetence on the part of OOCEA, RentAToll, and/or your rental company. The part that is unreasonable is the $25 processing fee for the violation. Unfortunately, that kind of fee is fairly common for things like this, photo red light or speeding cameras, bounced check fees, etc.
I at least hope you can figure out what happened so that you can keep it from happening again.
Good luck!