We’re sorry that Denoise and other features of the Photoshop Express Camera Pack did not serve your needs. The app should not crash, and we are having difficulty reproducing this issue. If you are willing to try something, then I have a suggestion. Some users report a possible solution to miscellaneous, inexplicable crashes of various apps (not just ours): do a full back up and restore of your device using iTunes. For some reason, this can sometimes put things back in working order.
However, if you simply want a refund, please contact iTunes Support: http://www.apple.com/support/itunes/ and explain your dissatisfaction and they may be able to accommodate you. This was an iTunes transaction and not something we can help with.