Thanks to all for the great info. We went to Walmart & Target to ask about the tracfone. They weren't sure which carrier they used. I saw online that one of there flip phones used cdma, which is Verizon. So we got that one.
One phone showed Quad-Band GSM/ Dual-Band WCDMA. I don't know what that means, but I thought that att was GSM, and Verizon was CDMA.
Can a phone use both Verizon and At&t? That would be news to me.
btw, we weren't locked out, the slide bolt inside the latch broke. We had to replacd the latch.