Justfab.com HELP

I recently ordered from justfab.com getting a pair of shoes for $10 and used express shipping making my total $19.95. That amount was already charged from my account January 31st when I ordered the shoes. Friday they posted a charge to my account for $39.95 even though I haven't purchased anything since the shoes I ordered on January 31st. Did I miss a fine print or something? Do they charge you 39.95 if you don't send the shoes back? Do they charge you a fee for being a member? ( which to me doesn't make sense because I've been a VIP member for about 6th months) OR could it be an honest mistake on their part? The transaction is still pending so I can't file a claim yet which is why I'm asking if any of you have experienced this or if I just missed something in the fine print. Thank you for any help!!