What should I do about car repair issues?

car problems with Mercedes We are having serious issues with Mercedes Benz and Express Oil Change & Service Center. Last week the check engine light came on in our 2011 Mercedes E350 and a lot of white smoke started coming out of the tailpipe. We did not drive it and had it towed to the Mercedes dealership. We checked the oil before it was towed, and it was fine. The dealership said that the turbo went out. Mercedes is saying that when they first got the car they had to put 2 quarts of oil in the car for it to even register on the dipstick and that the oil was sludgy. This is all not true, and if it is true why did the low oil indicator light not come on? They said that they need all of our service records. We took it to Express Oil Change & Service Center. Express Oil has all of our records wrong or missing. We took it to them on 6/30 for an oil change and they put the wrong mileage on the invoice (took it to Mercedes in August for new tires and the mileage was 1800 miles less than in June). Also, the invoice had our car information with the wrong name and other information. It was attached to another invoice that had all information for a 2009 Chevy pickup. Of course, the technician that did the work is no longer there (think that he was fired based on the way they were talking about him). We hope that they used the right oil. It calls for synthetic oil, which they charged us for and said that they put in. We also took it in October for another oil change and change of filters, which they don't have an invoice for. Please advise on what we should do.