yes you can.... if you look in the modifications area this has been gone over thousands of times already... if you have already unlocked your phone then you have to "revirginize" it first to fix the baseband on the modem... if you just unlocked, activated and installed 3rd party apps then just update and follow the instructions in the modifications area or on
www.hacktheiphone.com... that will get you back to a jailbroken, activated 1.1.1 phone.... as far as the VVM if when you hit voicemail it calls the number insted of showing the voice mails dial *3 on your phone and it should call the voice mail then hang up and go to the voicemail tab again and put in your password... then your all set.... please look around for the answers insted of just creating a new post next time.... Thanks