6 weeks ago I bought a 2012 car from a very large garage group, low miles, good price.

They said it would be ready to collect & pay for about a week later as they wanted to service it , valet & give it a new MOT! When I bought the car I noted that it needed a service for the DSG clutchs & the Haldex 4 wheel drive system, the selling garage was not an Audi dealership & i agreed that I would bear this expense & have done at a Audi Inside of my choice. So cut a long story short when I collected the car from Audi they informed me that the car has 2 decats pipes fitted in place of the secondary cats & it should not have passed an mot as its missing irrespective whether or not it passed the BET test! They also went on to say that the fact that there is no emission light lit then it has also been remapped to extinguish this ! They told me if I drive the car I could be liable for a largish fine or worse. I have contacted the garage who sold the car & could not get to talk to a manager but a salesman . I I have now looked at the Mot which was completed 2 days before I purchased the car & its been done at the garages in house Mot station....its 3 days since the phone call to them, no answer to my calls or emails ? What next ?