window etch rip-off?

Just bought an 06 Miata and the dealer insisted that the etching is
non-negotiable ... at a cost to me of $156! Lo and behold, when I took
delivery there was NO etching on my car at all. Since all the paperwork
was already done, the dealer tried to backpedal and give me 5
certificates for free oil changes in lieu of. I want it off of my loan
balance since I'll be paying the $156. plus 5.8% interest over the next
5 years. I'm working my way up the corporate ladder to get my $156
back. FYI, the salesman claimed I'd get a nice discount back from my
insurance co. because of the etching. Guess how much it came to? $7
bucks a year! Anyone else have a similar tale - and a resolution I can
use?