I am not assuming that it is nafarious, I appologize if I was not clear enough on that point. There are many possible ways it could be the result of a defect and you provided some interesting examples. In either case, it is a curiosity worth investigating.

Thanks for pointing out an easy way to disable imessage on iphone. Apparently after doing that iphone defaults to MMS. It still might be best to just turn off data and wifi.