It's been a while since I've touched a Fuji but I think the only way to do what you're talking about is if you're collecting ANI and using DNIS to route 800 calling (in conjunction with ACD). In that case you would be able to route calls from a specific number anywhere within your system.
In my experience telephone companies are also reluctant to pursue this unless you are willing to follow through with legal action.
Also, people who harass tend to be the type that, when thwarted, will find ways around your block, all the person needs to do is use a payphone to circumvent the work you put into blocking them.
I would suggest a 'friendly' reminder that utilizing the telephone to harass an individual is against the law and maybe throw in a little something about recording conversations. If it actually comes to that, a recording device can be picked up for under $100.