I know a few of these have done the rounds before but this one is from a founder of Skype and has succeeded in the USA.
It piggybacks the 3 network and the 'free' package is 200 mins/200 texts and 200mb data. The money make for them is the bolt-ons.
They are accepting signups now for testing before going live in the summer: https://www.freedompop.com
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