I had a problem where an android device I had purchased from eBay was "locked" after a week. I could still operate the device, but not connect it to a network.

I had a problem where an android device I had purchased from eBay was "locked" after a week. I could still operate the device, but not connect it to a network. It was apparently through the carrier with the IMEI and it didn't matter that I had a valid SIM that worked in the old phone. The phone was not carrier locked, but apparently, the old owner hadn't released it and could still make it dead/stolen. I went back through the seller, and they refunded the purchase and I got another that worked fine. They said it's a risk of buying phones from individuals even if you check status at the time of purchase. Luckily, I still had my old phone and retransferred all the data back over again and lost little except for a few calls/SMS messages.