Hello MissOCD,
Thanks for reaching out to Apple Support Communities. It sounds like you're having an issue with an Apple Pay update alert on your iPhone. We're happy to assist.
Were you able to complete the steps in the section "What to do next" in the article If you see an Update Failed or Apple Pay Not Available alert after iOS update or restart?
If not, the guide here can help with the steps for checking for any available updates: Update iOS on iPhone Be sure you have a backup before updating: Back up iPhone
Should the issues continue, get support by phone or chat, set up a repair, or make a Genius Bar reservation for iPhone, iPad, Mac, and more here: Contact Apple Support
Best!