I used Consumer Cellular for years ... lots of flexible options back then. I purchased older tech (new ... < $200 Iphones ... even cheaper 'droids, etc.). Just needed phones w/ modest data requirements ... everything is portable with a SIM card swap btw.
Awesome Customer Service ... they dropped T-Mobile as a network option ... lost me too
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I won't go into tech issues ... they ALL have warts
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But I was happy with CC for many years.... when I switched to T-Mobile my monthly went up 5 bucks to about $45.
I just need a phone (that works ... calls), and modest data ... per month. Speed doesn't freakin' matter .... FOR ME ... 2G - 5GUC .... for a basic phone that uses a browser. .. all are fast enough.
But the network stuff does matter ... when yer phone or browser doesn't even work, but if they work, then the network doesn't matter
Then shop for the cheapest option .... hth.