I reset old phone tor factory defaults but I still see my phone number on the set up screen.
I would say it is true on the 3G EDVO only devices. It wouldn't necessarily be true on the 4G LTE devices. If you leave the SIM card in during the reset, yes the phone will pull the number from the SIM card. If however the SIM card was removed prior to the reset, then the phone couldn't display a phone number as it has no way of connecting to the network.
Which phone model are you referring to?
I have multiple phones in the past and from my experience this is normal.
I second Ann's response. Even an inactive SIM card retains you phone number. Remove sim, then factory reset.
