Phone model is Motorola XT 912, initially in 4G LTE plan. I now realized I'm not using it as a web browser at all and just wanna avoid wasting dollars on monthly payment by using a T-mobile prepaid plan SIM card. The problem is: when I start the phone, it shows "This SIM card is from an unknown sourse", with a full-screen white background (notice it is not "the phone needs a SIM card to operate", which means it actually detected the SIM just can't use it). And when click "OK" and proceed, I cannot make any calls because it tells me "Outgoing calls are restricted by FDN". Also, when the screen is locked I see "Verizon Wireless|No SIM card." on top of the clock. So could anyone please help me with this matter? I'd really appreciate it.