1) It is hard to feel bad for you, as the odds of getting specific rarities is right in the game itself on the window where you open the shards. The chances of getting something good are ridiculously low. You knew what you were getting into when you spent that money.
2) You bought shards. Not specific champions, not guarantees of specific rarities, just shards, which *might* give you something decent. They didn't, and that's a part of the game too.
3) If you don't like the RNG of the shards, then STOP buying them. The only way to get them to change how the current system works is for people to stop spending money on the current system.
4) As others have stated, I will occasionally spend money on energy or bonus xp for events, but only when it is like a $5 pack for a reasonable amount. The odds of getting something decent from shards makes it completely unfeasible. With that said...
5) You gambled, you got poor RNG. Complaining to them about your gambling is the same as someone complaining in a casino about losing.
6) Your only option as already stated is to either stop spending on shards and trying to buy your way to the top, or dispute it through the app store. However, you will most certainly get banned for disputing it. While Plarium is severely understaffed for development, they make sure to have plenty of staff to ensure they don't lose money like that.
7) My advice is to not waste money on shards (aka gambling). Max out your mine, do the dailies, do the events (when they are feasible), and save your gems to buy the blue shard packs. I have heard many people say they got legendaries from blues more than they did yellows. Yellows aren't worth it, and if you look at the cost of yellow compared to blues, IF you are to buy anymore, it makes far more sense to buy blues. Your chances of a legendary per $ spent is MUCH better. Yellows are insanely overpriced, especially with how much trash epics and legendaries there are.
I wish you luck in future decisions, but again, you knew what you were getting into here when you bought the shards. Now, it's up to you how to handle that harsh lesson.