WAN is Wide Area Network, not Wireless Area Network
The term you are looking for is WiFi, stands for Wireless Fidelity I do believe.
Anyway, no matter what, you shouldn't be getting that slow of a connection. That's completely terrible. At the worst case scenario, you should be getting like 30-50 KB/sec. Not 4.
I'd call the ISP and ask them what's going on. How far away is the guy that's using your line, also?
We have 3 computers at home (sometimes 4) on the same DSL line, and it never slows down. How far do you live from the company's DSL servers?