They COULD be BS-ing you, but then they might not be. Odds are when you got your tint (or when the previous owner did), the tinting specialists probably extolled the virtues of "Metallized tint", in other words, because the tint has metal as part of its substance, it will not go purple. Now this is true, but this metalized tint can also wreak havoc with many car audio systems that do not have a fixed mast or retractable antenna.
So odds are, the tint could very well be causing your reception issue. If you know your tint is NOT metalized, or you KNOW you got specialized 3M carbon tint (a solution to the metal problem), then they are blowing smoke up your ass and thats not the issue. More than likely, the tint is the problem.
<img src='http://members.cox.net/inelson5/330i.jpg' border='0' alt='user posted image' />
<img src='http://members.cox.net/inelson5/wooani.gif' border='0' alt='user posted image' /> The whistles go WOOOO!!! *BUBB RUBB FAN CLUB*