Unable to delete texts on iphone?

I have an iPhone 5s and I have ios 7.0.4. Recently I have this problem where when I try to delete text threads on the messaging app, the app becomes super slow. Then I can't open any other texts or send texts to other people. So I reset my phone (home button and lock button held down) and when it turns back on I go to the messaging app and the text/texts I deleted are there again. I have tried restoring from backup and that didn't help any. Any help would be great thanks!

Not possible