I just bought a new Lumia 640XL. It works OK with my existing SIM, except SMS messages do not appear to work when sending receiving from overseas.

When I look at settings under Mobile & SIM, there is nothing there. My phone was delivered with a bunch of AT&T software. Could it be somehow blocked by AT&T? How can I unlock it? Though I can phone my contacts.... weird.

Just noticed there's also an ATT logo when I boot the phone.

UPDATE: rebooted the phone based on an answer here and can now see SIM settings. But I still see the ATT logo on startup. Can I get rid of that?

Thanks for any help

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