Hey guys, sorry for missing this post! Firstly, I’d like to welcome both of you to the Community 
I hope I can provide some clarity on this. When you make a purchase, the merchant first sends us a message that you owe them money. Due to the way Curve processes transactions, we charge the money from your underlying card immediately and the merchant has up to 7 days to take the money from us.
If the merchant doesn’t claim the money within 7 days, then we automatically return it to you. However, sometimes the merchant sends an Offline transaction to claim the money before 7 full days have passed. This results in the transaction being charged twice.
As mentioned, the transaction that isn’t captured should reverse automatically within 7 working days. If you get in touch with our support team they can sometimes speed this process up for you too.
I understand it’s not the most straight forward process but unfortunately we have no control over merchants sending offline transactions. But, I have flagged this with our team so that they can work on how to improve these situations going forward.