The best I can do is point at the topic here:
http://support.nabble.com/Remove-ads-Payment-settings-td7597704.html#a7597708However, the weird thing is, I've just noticed that the "Cancel Payment Subscription" link has gone missing from my profile screen on that forum, but ads are not appearing. I've no idea if that means my card won't get charged in future or the ads will return.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.