Registration of car with seller's personalised plates

On the 25th January we sold a car with personalised plates, and we were told it will be returned to us within a week. We still don't have our plate, whats worse WBC have now registered the car in their name (as they should) but with the personalised plate. Their natis department is careless and everyone involved in the process dropped the ball. I still don't have the way forward, I will definitely not wait for the car to be sold first, you guys need to get a new plate for the car so you let go of mine. This is a mess as anyone can take our name now