Hi SH91,
We understand you're running into a billing issue preventing you from downloading apps. We recommend starting with the suggestion below to ensure your on-file payment method is updated: If you can’t download or update apps on your iPhone or iPad - Apple Support
"Add a payment method
You might need to have a valid payment method on file, even if the app that you want to download is free.
Add a payment method"
You'll find a few other steps in the link above, but updating your payment method would likely be the best path to resolution. If the issue persists, use this link to check for options to reach our billing team: Get Support
Kind regards.