Misleading Treasure Upgrade

I am user of the 106604111594000544033 iD. I would like to make a report. I had just earned a treasure chest of Ancient Dark Spell. It tells me that I could upgrade it for 30 Power Stones which I already have at my disposal. When I clicked on it, surely enough it did upgrade. But my Souls were subtracted instead. Around 400 if i'm not mistaken. This is clearly misleading since I intended to use my Power Stones alone....please undo this mistake