Why can I not call out on my Galaxy S3 phone using Consumer Cellular?

A

AC Question

Just got my first smartphone. Received a SIM card from Consumer Cellular, but after
inserting the sim, powering the phone up, I cannot make a simple phone call.
Talking with CC support did not resolve the problem before battery went dead.
After re-charging, and learning a few more things as I go.......... I found at top of the screen that there is a circle with a line through it - meaning NO SIGNAL?
Also see symbol that has a ? mark in it ....... which means SIM card is from unknown source?
Note that I can get internet (from my Laptop internet provider), AND that I do have another phone on Consumer Cellular and I can get signal (make calls) on that.
Also note that seller of my Smartphone said was GSM UNLOCKED. CC support person took a long time and never was able to verify that it indeed was unlocked!
Any help would be appreciated.