Answered question
I am already a fizz user and recently my phone died on me, so I wanted to switch back to an older model (I went from a Sony Xperia 5 to a Samsung Grand Prime, if this matters at all). When I put my FIZZ sim card into the older phone however, it tells me the sim card is locked. To be clear, this is a FIZZ sim card. I have never ever been locked to a carrier (not even with past carriers, I have always bought my own phones and had it unlocked). What is going on and how should I attempt to fix it?
Any advice is welcome.
The phone is locked to the previous provider. Samsung phones tend to give more confusing messages than other brands when they're locked. Oh, and samsung phones tend to lock to the first sim card you put in them.
Other answers
Did you try to update the phone?
Things I tried so far: I checked compatibility of frequency/bands (seems fine) and restarted the phone with SIM inserted. I'm not sure what updating the phone itself means, however.
In the Manage section of you account, there's a thing called Unblock SIM card, I don't know if that would help!
Did you try to use the PUK that you find on your Fizz account? Use it only one time.
Updating the phone means downloading the last software Settings -> Software update -> Check for updates.
To simplify this process in the future, write down your PUK code and keep it somewhere safe.
What ALLISON says is correct. Most Samsung phones will lock to the carrier of the first sim card you put in. A quick search, I found this: http://unlocky.net/samsung/how-to-unlock-samsung-galaxy-g... I don't know how trustworthy it is, use at your own risk.
@Code_KRUEW: I did not know that, for my A50 does not work like that, but probably is a different FW. I already inserted 3 cards without problem.
Thank you so much to everyone who answered!! You guys were right about Samsung! I had never had a locked phone but I guess it must have just locked with the first provider I'd had in there. So annoying. But resolved now. Thanks for your help!