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Unlocked phone "Not registered on network"


Sep 7, 2020
I bought an unlocked phone online from Amazon for my mom. I took the sim card from her old Galaxy S7 and transferred it to the new device. All apps, contacts, texts, call logs, etc were also transferred. I try to make a call, "Not registered on network" is what it says. I think the fact that it's unlocked has a lot to do with the problem. Me & my mom both use Boost Mobile. I swapped my own devices before and it was simple as just transferring data & the SIM card but neither of the two phones were 'unlocked' they were both Boost carriers. What am I doing wrong?
I believe in the US, you might have to register the phone's IMEI, ESN, MEID, etc. with certain carriers for them to activate it on their networks.

This is Boost Mobile's BYOP site.

AFAIK it's only the US that does this, in most other countries you can just swap SIMs, and use pretty much any phone you like on any network.
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In addition to what @mikedt said, if you've had that SIM card for a year or more you'll probably need a new one.

Boost used to use the Sprint network, but now they use T-Mobile. I doubt they will still activate one of their old Sprint SIMs in a new phone since the Sprint network is being dismantled.
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