Are you saying someone cloned your motorbike numberplate and made a car numberplate?
That's not cool, but I wouldn't worry if I were you, you said it yourself, you don't own a car, so unless they can prove with it with an e-Natis document that you do own a car, I would just ignore it.
If someone wants to prove you are wrong and CAN prove you do own a car with that plate, tell them they can sell your car, deduct the etoll amounts owed, and pay you the rest out in cash.
Win Win situation.
