Well that's the whole problem with Radio Shack these days. As fads either end, or become mainstream (in which case every other store sells the same products), Radio Shack loses out.
If you're buying new wireless service these days, the best place to buy it is at Costco, for a lower price, and better warranty than the carrier's own stores or from Radio Shack. And Costco dedicates about 75 square feet to do high volume sales from three different carriers. Radio Shack has high cost leases and the expense of stocking a huge number of low price SKUs that few people buy.
Radio Shack is adding wireless-only kiosks in some places, but it's too little too late.