If you'd like to get your $120 back, go for it. You certainly are on the high ground here, though it unfortunately becomes more difficult to get money back than withholding payment up front until the matter is resolved. Their attitude stinks, and it seems pretty common with a lot of service companies like this that don't seem to give a f***.
But I also think it's no big deal if you don't want to pursue it any further. Strangely enough, I've found that many times these things work out in odd and beneficial ways in the future, particularly when I've extended good will even when none is due. I can't count the number of times when I've let something like this go, only for it to work out 10x in my favor in the future. For example, one day you'll be attempting to sell your home, and the ideal buyer will come along and say, "Oh man, you've got the 4" hypoallergenic filters, just what we need -- we'll take the house at full price!" Obviously that's a dumb, made-up example, but these things seem to happen often, at least in my experience. I'm a Christian, so I have my own beliefs why this happens, but you can apply your own belief system (karma, Tao, bogus law of attraction, whatever).
