How to Unlock Your Nokia Cell Phone. Typically when you purchase a cell phone, the company that sold you the phone (ex: AT&T) locked the phone before you bought it, so you can only use it on their network. Follow along after the jump to learn how to unlock a Nokia phone.ypically when you purchase a cell phone, the company that sold you the phone (ex: AT&T) locked the phone before you bought it, so you can only use it on their network. Follow along after the jump to learn how to unlock a Nokia phone.