The codes I use for Anonymous Call Rejection are:
*227# to activate
#227# to deactivate
*#227# to check if operational
Worth mentiong ACR only blocks calls that are 'withheld' and not calls that are 'unavailable' and I believe these codes don't work on all VM phones - perhaps something like ex C&W exchanges or something equally technical like that
It is free of charge for me and always has been. I turn it on and off all the time, depending on circumstances.