You can just tap on the plate to adjust. The system does remember your previous purchase details as it's connected to your device, however, you are not locked into using the same vehicle forever.
You just tap the plate area and it will allow you to adjust the license plate accordingly.
If you paid for the wrong vehicle, please repay for the correct vehicle ASAP and then let support (support@honkmobile.com) know so we can issue a refund for the incorrect purchase.