Arrrggghhh test mode

I have been notified that I have made a sale through my shopify website and that the client paid through Amazon, but my Amazon account was in test mode at the time? I can find no indication on my amazon account that a payment has been taken. It wont allow me to refund her payment. I don’t want to lose the sale but also don’t want to lose product or a customer.
Any Ideas?

Thanks in advance

My recommendation is ship that product to your costumer, because starting a business is hard and you shouldn’t lost a costumer for your mistake. This also happens in other businesses for example Ryanair, by mistake sometimes made flight tickets just for 1euro, and people bought it so they lost money but it is what it is.