Here is a list of USCC prepaid phones (available at WalMart, in USCC markets) I have found to be completely SIM unlocked out of the box.

The only service these phones cannot be used on is USCC postpaid...

hotpepper Serrano $15.00

TCL A30 (was $20.00, now $25.00)

moto g PURE (was $30.00, now $35.00)

The Samsung Galaxy A03s was SIM LOCKED, and could not be easily unlocked via 3rd party means. The 3rd party unlock available was where you had to put in "16 zeros" after restart/power cycle.

I am wondering if anyone has tried any other USCC prepaids to see if they are SIM unlocked out of the box...

Such as the new TCL ION Z...?