We are glad to let you know that we have fixed the issue you reported.
We have added the Order Number field to the vehicle details page, so now our users can control order of appearance of the vehicles on the my account page and use that order number as last parameter during SMS submission. Our system will post fill-up to the vehicle with order number submitted. If somebody has only 1 vehicle - there is no need to submit order number, old format stays intact.
Also we made a Mobile Phone field on the profile page to be able to accept a comma-separated list of phone numbers, so it's now possible to associate many mobile numbers to one account.
Thanks again for your suggestion and have a great day!