Brake Light On problems of the 2001 Mercedes Benz SLK320

My brake lights are defective; they have been repaired several times but after a few months, they stop working. I have this car since 2006 and have been told this was a recall issue. But when I went to autobahn motors in belmont, CA, they refused to repair them. I was told by another mb dealer that the recall was finished and by another that they had been repaired at some point (?); I understand that it is not the brake lights themselves but some mechanism that was faulty and that has to be replaced. I cannot afford to have them repaired every 3 or 4 months and feel mb should do it since it was a recall and the lighting mechanism should stay fixed.