My R350 Benz

I have an issue with opening my R350 Mercedes Benz 2006. The remote and the manual key will not work, I thought it might be the battery and changed it but I'm still encountering the same problem. Moreover I have started having problem with this car now for the pass two weeks. First I was transmission fuel linking, then the truck door does not stay up unless we hold it up, the heater unit is not working and now the key problem. The trunk, heater and key issues started after taking it to the shop for service. It was unbelievable the way I was treated at the dealer's in Silver Spring repair in Maryland. Now all this is going on. I need help to know how to get the car running foremost then I can deal with the other issues, Need the car to commute.