Go to settings > general > about and see if you have carriers listed. I
had T-Mobile as the primary carrier and Visible as the secondary
carrier.SMS text messages did not work for me, but iMessage did work.I
had to back up my phone, Reset back to fac...
OK, texting works for me now. I had to backup my iPhone, and then erase
it back to factory. Then inserted the SIM card back in. I had 2 carriers
in my settings, T-Mobile and Visible. T-Mobile was the primary. Now my
settings just list Visible.