Deleted all my photos, still taking up the same amount of storage

My phone needed more free storage space to do an iOS upgrade; my ~3,000 photos were taking up 70GB so I deleted about 1,000 (and cleared the recently deleted folder). They were then somehow taking

up 71GB. I’ve tried everything - disconnecting from iCloud, to iCloud, deleting another 1,000 or so photos, restarting. Everything either has no effect, or the storage used actually goes up. There are *not* 70GB of photos on this phone but I can’t budge the number. Is there any way of fixing this?