Nokia Lumia 820 - I get payment authorisation failed for my Nokia MixRadio+ subscription.

You need to go to account.nokia.com and remove your card.If you wish to continue your Nokia MixRadio+ subscription, add another card and re-subscribe to Nokia MixRadio+.If you wish to cancel your subscription, go back to Nokia MixRadio and go to Settings > Nokia MixRadio+ > cancel subscription.