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?