Fail to send messages

I have the same problem... iPhone 6s and text messages to certain people won't go out. I always get 'Message Send Failure.' I've tried a few different suggest ways I found online, but what seems to work each time, whereas the online suggestions did not, is to call the person (voice) and have them text me first (which is a real pain btw), and then I can text them back. Not sure why this works, but it has worked every time. I'd really rather Apple or someone tell me how to make my phone work other than "Turn this off, then turn that on, then Reboot the phone, then turn this back on, and that back off, and then see if you can send Messages." Seriously, that is almost exactly what it came to and even after getting my phone to work (but only some of the times) the next time I sent that same person a text, I had to start the whole sequence again. That is how I figured out the whole have them text me first thing. I was just about to try to get my phone to work for like the fifth time when 'they' texted me, and voila I could text them (for that session at least).

Thoughts?

If you do not have data then you will have to connect to WiFi