I dont know if it was a bug or not but i undrestand you can buy decks in game,
And what i did i had around 8.23 Euros in my Battle net Balance and 7 decks cost around 9 euros but at that time i was not aware i had to little cash on my balance.
So isted of telling me that my balance is to low and i cant make that purchage and letting me know it want to access my paypal account it went by it self and took the money from my paypal/bank card it was coneccted to .
So i dont know if it was ment that way or now but its not cool taking the money from paypal with out asking first!
Sorry for bad gramma .
Greetings Mohammad R.