Hello my name is ***** ***** I will be happy to assist you.
Were you making this purchase through the itunes store?
Try going through the following steps on your phone.
Tap Settings > iTunes & App Store.Tap your Apple ID, then tap View Apple ID. You might need to sign in.Tap Payment Information. If you're using Family Sharing, only your family organizer can update the payment information.Change or remove your information. To remove your payment method, select None. Get help if you don't see None or can't select it.Tap Done.
If that still gives you an error message then do the following. Click this link https://support.apple.com/en-us/HT201266 next go to the bottom of the page and click contact itunes store support. Next click click "Purchase, Billing, Redemption" Next click Itunes store account billing. On the following page you will have the option to contact via phone or email so choose whichever you prefer and explain the exact message you are getting and they will fix it right up for you.
Sometimes when changing a card their can be a hold on purchases for security reasons, this could be the issue if the above does not work.
If you need more help let me know and if you have a moment please rate using the stars.