For several months I've been getting calls with spoofed Caller IDs. I
> understand spoofing requires either VoIP or a PBX system with DSL.
No, you could do it with ISDN too. There are dozens of ways to do it. Caller ID information is not reliable.
Can anybody with cable internet access and suitable software make VoIP > calls?
Yes.
The other day I received a wrong-number call from an exchange belonging
> to Level 3 Communications. Among other services, they offer residential
> VoIP services through wholesalers such as ISPs and cable operators. I'm
> confused. Does a consumer need these services to use VoIP?
To use VoIP, you need an account with a VoIP provider, you need a VoIP box in your home, and you need fairly wideband internet access. It is very profitable for the ISP to bundle the VOiP services along with the rest of their services, and outsource them to a provider like Level3, just like they outsource mail and news services in most cases today.
--scott
"C'est un Nagra. C'est suisse, et tres, tres precis."