iPhone storage showing full even after deleting photos

Did you also delete the photos on your iPhone in the Recently Deleted folder?

Before you do, make sure to transfer those photos you want to save to your computer.

If you are using iCloud Photos, deleting photos on your iPhone will also delete them from all other devices and iCloud.

Archive or make copies of the information you store in iCloud - Apple Support

Photos will occupy space until they are permanently deleted. (Once they are permanently deleted, you can’t get them back.)