How can I efficiently process product exchanges on Debut?

Hi Miles - So what’s the best way to exchange an item - I’ve posted this elsewhere as well, and the Shopify staffer responding there has asked us NOT to unfulfil and edit orders.We can’t sell a product at a 100% discount after refunding the old one the tax rate for our product in our region is based on value. Under a INR 1000, it’s 5%. Over INR 1000 it’s 12%. So what’s the way out for us?