missing purchased simoleons

I purchased 2x £10.99 packs of Simoleons. We used a gift card for £15 my son had (it's his game) We put it through twice by accident.  It has taken the payment for the two packs which I have received email confirmation for but the amount of simoleons he has is far two low for two packs.  I also didn't have enough on the card so it took the payment for the extra amount from a MasterCard I think is mine. I'm not sure how this was possible as it was all done on my sons iPad which has restrictions on it and we didn't approve a card payment. How do we get the missing simoleons?