That's strange maxjacknasty, since VISA/Debit VISA is one of our accepted payment methods.
Perhaps try using a different browser and an incognito or private window to see if your purchase goes through then. It'd be worth making sure cookies are enabled and that ad blockers are disabled while you give that a try, and also trying a different network or mobile hotspot. If you have a credit card, I'd give that a try too.
Have you tried paying after removing the payment method from your wallet? Or alternatively, adding a payment method before checking out? Another option would be to try adding funds to your EA Wallet, then paying through that instead.
Let us know how that goes, thanks!