How do I get rid of saved messages on iOS7?

I noticed this new feature in the Usage section of Settings. I have a whopping 8.8 GB of space taken up by Messages (always wondered what that "other" data was...). I tried getting rid of it by deleting conversations in messages (almost all of them, and especially the ones I knew had a ton of pics and videos in em) but after doing that and reopening the app, ALL my messages were gone. I didn't delete ALL of them. I restarted and then all my messages, even the deleted convos, were all back. How can this be??? I did this twice and the same result happened. Oddly though, my message data number went down by a few points to 8.2 GB.

I seriously need to get rid of these saved messages so I can reclaim my phone space and deleting them within iMessage doesn't seem to be doing the trick. Has anyone else noticed this happening? If so, how did you fix it? I figured I'd try asking here first before I go to the Apple store this weekend.

Please let me know if you have any suggestions. Thanks!

Pooja