You know wha you did!
Just kidding! You need a new A-Key, Verizon tech reps are morons when it comes to this. Call back in and say you hard reset our device, NOT FLASHED A NEW ROM! Say when you try to make a call, you get an error saying whatever it is, probably "unable to authenticate the call." If they don't understand when you tell them that, and they don't figure it out, mention the A-Key. The rep will then realize they are doing the wrong job, and say, "huh? wtf is an A-Key?" Then you tell them to ask around, and eventually you should be good.
What happened was, your A-Key was wiped out after the radio flash, Verizon needs to reset it, just make sure you say you had to hard reset.
Samsung Galaxy Tab