Navigational (global Positioning System) Gps problems of the 2002 BMW 330

I have a 2002 330ci. I have had so many issues with the navigation system from the time I drove it home I get a popping noise when the navigation tries to mute the radio. I also cannot adjust the navigation volume at all. In addition when I turn the radio power off the navigation volume comes on at a very high volume level. I have been round after round with the BMW dealership and customer relations the executive office, etc. BMW has been useless. After replacing numerous parts and multiple weeks in service BMW has only made it worse. The BMW regional rep has now officially called this "a normal function of the system. " BMW has given the run around because they say they do not have a fix. I have spoken to so many people most who have promised to follow up and never did. I have tried everything but have just been given the run around. The technicians have heard it and admit it is bad. My car has been logged in at the dealership for over 35 days over two years to try to resolve the issue. I have even asked BMW to 1. Remove the system and give me credit for it, they have refused or 2. Update the system to a newer version that does not have the issue, they have refused. I am now two year into a three year lease and need this resolved once and for all.