You had the app, you upgraded the OS. There is never a guarantee that the app you bought and paid for previously will be upgraded to work with the new OS. This is not just an Apple thing. Yea, sometimes it *****. Sorry if this is the first time you've ever noticed it, but it't quite normal.
I may not recall all of the features of iPhoto on iOS, but it seems to me, many if not most of those have been migrated to the Photos app. If so, you really haven't lost anything; again, I don't know all of the features. However, Apple sometimes removes features and whole apps over time (e.g. on Mac OS: iMovie lost features, iDVD hasn't been updated in years, iWeb is gone, future development of Aperture has stopped, various apps of the iWork suite lost features as they were being upgraded the past year, etc.). Apple also said in the Keynote I referenced that iPhoto on Mac will go away and be replaced with a whole new Photos app to mirror the iOS features (some time next year if I recall). This is the march of technology. The license fee you paid for the iOS 7 version of iPhoto was spent and is gone. You used it. It doesn't work any more on iOS 8. Use Photos instead. Photos along with iOS 8 are free. In fact some time after you paid for iPhoto, Apple made it a free app with purchase of a new device. I never paid for iPhoto on iOS. It came free with my device. Maybe they don't do that outside the US yet? Not sure.
Who can you talk to? Call Apple and complain. I'm sure they'll listen and point you to the new app with additional features, which you got for free with your free iOS 8 upgrade.
