I see that once you click the "Visa/Mastercard' icon and click "Buy Coins", There is the Discover and Amex logo on the top right of the pop up where you enter the card details. I've tried my BoA card but I keep getting "Transaction wasn't completed" and I've also tried contacting PaymentWall but they haven't replied back yet.

Has anyone else tried using Amex/Discover? If so, I can just run to the store and get an Amex gift card and hopefully, that'll work.