How do I change my lock screen name?

My brother got a new blackberry passport so he decided to give me his z10, I changed the device name, blackberry ID to my name but the lock screen still shows his name... how do i change the lock screen name from "Devinder Shergill" to "Guntaas Shergill"?. Thank you.

System settings, security and privacy, lock screen, lock screen message.

Though you should really wipe the phone and use your own BBID.

thank you :)