Cambridge Repairs CC

I bought a Groupon for Cambridge Repairs CC in order to get my car serviced and repaired at the same time. It has now been 3 months and I have received my car back for the 6th time, of which the latest stint they had it for over a month, and my car is worse than when I first took it in. They were fixing a cracked gasket, and now my engine light is on, my revs are dropping and the car drives and sounds terrible. On top of this, they have done 1100km's in the time they've had my car, and they have worked on my engine where no consent was given. My car is now not drivable, and I cannot take it back to them because they are doing more damage than repair. They also will not refund even after taking the above into account. Now they ignore my calls or tell me they are too busy to talk. This reflects badly on Groupon as I trusted your site to not guide me to such bad service. I emailed this to you last week and am yet to get a response. Please send me their holding company information, they refuse to, so that I may escalate and resolve the issue. Please also leverage the company to refund me for services not rendered, or pay for my bill when I take it to another dealer to fix their damages