If you already have a number plate payment or an eTicket for the vehicle, you cannot create a Toll App.
The same applies if a Toll App has already been created for the vehicle.
If an eTicket or a number plate payment has already been created for the vehicle, or if a Toll App has already been created for the vehicle, you cannot create another Toll App.
You can log in to self-service and cancel the number plate payment or the eTicket. Read here how.