Hey JonD,
If I understand correctly, you were able to block emails, but you still receive junk mail and it is asking you to unblock. Is the junk mail saved as a contact? Are you using an iCloud email account or another provider? It looks like you have already done some troubleshooting to solve this issue. Even though there is a chance that you've tried these steps already, I would recommend you follow every step and let us know if the issue persists.
If you're in the Mail app, open the email that has the contact that you want to block, then tap the contact at the top. Tap Block this Contact."
Block phone numbers, contacts, and emails on your iPhone, iPad, or iPod touch
"To mark a message as junk:
- On your iPhone, iPad, or iPod touch with iOS 7 or later, open the message, tap the Flag at the bottom, then tap Move to Junk."
Identify and filter junk mail in iCloud
Please don't hesitate to let us know if the steps resolved your issue or if you need additional assistance.
Thank you for using Apple Support Communities. Have a good one.