In case you are traveling and rely on your phone for boarding passes, or you are traveling and having problems reaching family at home via their cell phones, our local news reported nationwide problems with AT&T, Verizon and one other (that I think is TMobile). Phones apparently displaying SOS on screens, but local news say one can still dial 911. We are Verizon and our phones are still working.
Check your local news to verify and follow.
UPDATE:
Just heard a bit more on Today Show...apparently you might have service one minute and then it can show the SOS the next....one of the anchors had experienced that.
So, just know you are not alone, if you are experiencing this.