Sorry to hear, I've heard it can be a 50/50 if they will refund you or not, my aunt had the same thing happen, kid spent like £200 on a game an kids tried to say it wasn't them but it clearly was, apple couldn't care less an just told her maybe put a password on it next time, however I have heard of people getting money back if the kid has paid for somthing from games
I hope you get your money back but unfortunately it's going be entirely down to them if they want to, if the game genuinely is glitched an they refuse then you might be able to take it further but you would need proof that it was actually bugged to do that, I'd say maybe record it happening, but if the kids have just said it's glitched then unfortunately nothing you can do if they say no as they will just say the same as they told my aunt an that was to put a password on it
Games now a days are getting ridiculous, as a gamer myself an I do have some mobile games it's insane how many will have these pops ups like starter kits an "this pack was £1000 but you can get it for £50" an they have timers on them, it's so easy for kids now to click on it an then as soon as they do another one pops up with a countdown on it, an the kids see what they get an want to buy all these in game things an as soon as they run out there's more pop ups advertising more "great deals" I can see how it would all rack up in price an before you know it the kid has spent hundreds, most mobile games are basically pay to play now, if there's a option on your apple device to click don't allow in game purchases I'd click that, it's android I have so not sure what apple has