Device unlock

I am trying to unlock a device (Moto G Power) which is paid off months back. I got a new sim from Tello and the number is already ported. However, when I put the new sim in the device, it says it is network locked and asking for an unlock code.

I called the Xfinity agent, and they opened a case. After 2 days, they closed the case saying the device is already unlocked. But it is not. I tried restarting the device, but it still comes up with "network locked" message, and asking for unlock code.

Looks like many other customers are facing similar issues. I never faced similar issues with any other network providers. What is wrong with Xfinity?