Overcharged when using Curve on Ebay

Hi all,I linked my debit card to Curve and used it on an Ebay transaction that totalled 16.78 (1 basket that has multiple items from multiple sellers). My Curve app and my bank account showed that I was charged 27.44 for this transaction. My Curve app then showed I was also refunded for the over charge (This refund has not shown in my bank account yet). My question is how and why did this overcharge happen? Ebay customer services said I was only ever billed 16.78 from their side, yet my bank account and my Curve app show the charge of 27.44

Last time I had something similar Curve customer service told me the transaction had failed and refunded immediately, then tried again.
You will see your refund in about 3-5 working days.