What album did you delete the photos from ? If an album that you've created yourself in the Photos app then deleting the photos from there won't free up much space as the photos weren't in the album, they were effectively just pointers to the original photos (not separate copies of the photos). If you mean that you've deleted them from the Camera Roll album have you also (depending upon what iOS version is on the phone) deleted them from the Recently Deleted album, and if you have, tried doing a soft-reset/reboot of the phone to see if that frees up the space ?
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