Default Store demo phone still active

Ok I bought this phone off of ebay with a broken screen and a bad esn. I fixed the screen and turned it on and the note II retail mode app was installed and I couldn't do much with it. I assumed maybe that was why they thought it was a bad esn so I rebooted into the bootloader and factory reset it. When it came back up everything seemed ok so I went into the settings to grab the esn to check and it showed it was on sprint and connected. So I made a test call and it went through. It would seem they sold the phone when the display crapped out, but never deactivated it. Has anyone come across this before? Could I have a never ending sprint line?