Cannot delete text messages
I have been having a reoccurring problem deleting conversations and messages from my iPhone. This began with my iPhone 4S, and has carried over to my brand new iPhone 6.
Whenever I delete a single conversation, my phone begins to slow down, and my messaging application quits unexpectedly when I use it. After some time, or restarting, the messaging app works again, but the deleted conversation is back. Deleting multiple conversations not only slows the device, but also keeps any messages I've been sent, iMessage or text. As soon as the phone has been restarted, all of the conversations have returned.
I have gone to Settings>Messages>Message History and set it to 30 Days, but that has not deleted existing conversation. I also do not back up my messages to the cloud as far as I can tell.
Thanks in advance.
iPhone 6, iOS 8.1.2, Carry over issue from 4S