New iPhone6 not sending SMS (error), but receiving ok.

Just got 2 new iphone 6's in the house. (replacing iphone 5's). We are on VERIZON network. Texts via imessage seem to work fine. They are both having problems sending texts to other people that do not have imessage. Occasionally they go through, but that was once all day so far. We are having no issues receiving texts from those people. That part works just fine, we just can't reply. Usually it just says Not delivered with the red !. It pops up almost immediately when trying to send it. Now, we had a pop up that said "No SIM Card Installed" when trying a text. We have iMessage turned on, and we have SMS messages turned on. This is very frustrating, any ideas? Thanks!