Unregistered vehicle

Purchased a car from we sell cars in February 2017. In October 2017 the license disk was about to expire for both my cars, the post office told me that I cannot renew my license as the vehicle I bought from We Sell Cars didnt go for road worthy test, therefore they cannot renew any of my license. Now i am stuck both my cars cannot get new license disks because of incompetence, yet after contacting them they refered the issue back to the sales consultant, we sell cars arranged for my car to be collected, three weeks after they claim they took my car for registration i am still stuck without registration. The worst service one can get, you call them to highlight on their mistake they still make another ******** mistake again