My credit card is declined

Apple ID payment information - If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store

If necessary, contact iTunes Support. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option.  You may need to pick a problem that is slightly different than yours to get a chat option.  

iTunes Support

iTunes Support – world wide

rikoby Said:

"My credit card is declined plz help me: I can't add my credit card to my apple account for some reason..."

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Battery is at 1%:

For Note: Seeing 1% battery life on that image you had provided, there may not be a sufficient amount of battery power left to complete this transaction, having to go through so many servers. So, charge you iPhone's battery for a bit, then attempt this once more.

MalwareBytes for iOS:

Run MalwareBytes on your iPhone and see if this anything is found. It is developed by long-time Apple Users, and is highly-efficient in detecting Malicious Software Apps (Malware). Download the iOS version from the App Store. Install it > Update it > then Run it. Remove anything that is found.