Ey, not nice to get a new shoe on the feet and have a terrible time with it. You should be able to take it back to the store, though. Even if you've done a few km in it. I know Sweatshop, for example, have a 2 week no-questions-asked policy and I've had no trouble with a few other stores when it comes to returning a shoe. It's just not worth it if you're going to dread putting it on for a run. That said, have you tried different lacing techniques? My Adidas Supernovas caused the exact issue you described. I laced them to the point that they didn't even cover the lower outside of my foot. I also cut the tongue out, removed all the foam and unnecessary padding then took it to a cobbler to sew back in. It was a definite improvement after that. Don't be afraid to hack a shoe to fit your needs.
