Hey asqual,
It appears that you've received an email telling you that your payment for additional iCloud storage was denied, and we're glad to glad to provide assistance.
Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support -- First, make sure the message you received wasn't a phishing attempt. If you're ever unsure if a message you've received is from Apple or not, never use the links in the message or provide any personal information in reply.
Identify legitimate emails from the App Store or iTunes Store - Apple Support -- This article explains how to determine if the email you've received is legitimately from Apple.
If you think your Apple ID has been compromised - Apple Support -- If you ever make a mistake and provide information you shouldn't, use the steps in this article to secure your Apple ID.
If your payment method is declined in the App Store or iTunes Store - Apple Support -- You can check your purchases to determine if your payment method was declined. If it was, you can fix it using the steps in this article.
Feel free to get back to us with any questions or problems you may have.
All the best.