Mercedes-Benz of Pompano

I just had the car for 3 days and a very loud noise came from underneath the car . The salesmen frye's to convince me that it's normal and heard it on orher vichles. I mentioned to him that I have been a client of Mercedes for over 12 years & I don't believe it. Besides most of my close family all have Mercedes & Porche. I spoke to a young gentleman and he came in the car and heard the same noise .We pull in to the service and Tom the chief machanique comes for a test drive and agrees that the noise is not normal . He speaks to Brad the service Mgr. and immediately request for me to bring in the car first thing in the morning. Tom cfm. to me that a request be made for him to fix the problem. Brad was very kind and the next morning Tom repaired the problem in 25 minutes. The salesmen should listen to their clients rather than pushing me off . I have a bad experience but the service staff Brad & Tom should be highly commended for taking the time to listen to my concern. I realize it's a 2016 & not new car. I paid it cash and had intention of switching the car to a E 2 dr coupe on my 65 birthday in 15 months. I definitely will not deal with the same sales person. The rating I give is for service because sales receives a 0