I am unable to delete whole texts from left-swipe. i click delete and they dissappear. But then i can't send or recieve texts. i reboot phone and deleted message reappear. i've synced, backup, everything. Help!

I am unable to delete whole texts from left-swipe. i click delete and they dissappear. But then i can't send or recieve texts. i reboot phone and deleted message reappear, but i am able to continue send/recieving texts.. i've synced, backup, everything. Help! I am doing this beacuse in my space on my phone my doucments and data are taking up 9GB of space, and i don't know why other than in my phone it says messages are taking up 8GB or so. I am running ios 7.0. I have synced my phone with itunes, backed up, reboots after deleting the texts, they never vanish, i have even restored from itunes and restored from a backup that didn't include the texts after i deleted them.