iTunes Store says my card is invalid
You need to check your subscriptions or recent purchases for an outstanding charge made to your account.

Check your subscriptions on your iPhone/iPad/iPod touch- https://support.apple.com/en-ph/HT202039

Check all of your recent downloads by visiting:
http://reportaproblem.apple.com and signing in.

If both subscriptions and recent purchases arent showing a charge then you should contact AppleCare via 1-800-MY-APPLE and ask to speak to iTunes. You should expect a 15-25 minute wait since iTunes is always busy. If you can call in the morning between 8am-11am, not too many people call Apple that early.