I don't know about AT&T and T-Mobile, but Verizon and Sprint (CDMA) phones have the IMEI/MEID tied to the phone since there's no SIM. It works a bit like a VIN

I don't know about AT&T and T-Mobile, but Verizon and Sprint (CDMA) phones have the IMEI/MEID tied to the phone since there's no SIM. It works a bit like a VIN on a car I think. This means they know what phone you're activating during activation.