My phone says that my SIM CARD IS LOCKED.

[Android Central Question]

I had an LG phone and upgraded to a Samsung 7 flex and the phone worked for a couple days then the SIM card locked

 

[Rukbat]

That could be the phone not reading the card properly, the card being for a different carrier than the phone is locked to or the particular phone being blocked because money is owed on either the phone or the account it was on. (I won't get into "or it's been reported stolen".)