I have a PBX (Asterisk) I setup as my main/primary/only personal number. That number is given out to anyone who needs it. The beauty of this is, no one has my personal cell (or other) numbers. This makes it very easy for me to block any spam numbers. In fact, I inject the FCC telemarketer spam caller list into the system blacklist. I also have it setup that the caller needs to 'press 1' to reach a human. It's not exactly hard to setup, but is certainly not for non-technical folks. However this system has given me the control over my phone number, callers, and spammers.