Q: Extra storage paid for but still cant save

Hi,

I think you are confusing with an iCloud storage. The only storage you can buy is at iCloud. To free some space from your device you should move your photos into iCloud.

You have free space on iCloud not on your device. so first need to move your data from Phone to iCloud. When you see the free storage on phone or device then it will be store your photos.

Just simple manage your all data or stuff on icloud after that you can delete from device here is the steps to manage data on iCloud

Manage your iCloud storage - Apple Support