Hey Mouldybone,
You wouldn’t be able to buy this more than once on your account, so it’s unlikely that you actually bought this pack 3 times. You can review your account’s transaction history for more information: https://account.battle.net/transactions
If your bank account shows more than one payment, it usually means that your bank has put on hold the funds for these transactions. The funds for the purchases that didn’t go through will be returned by your bank, to your bank account within 2-3 days.