[Skunkworks] Safaricom modem nuisance

Hey guys, I have a problem over here. Some of my staff aren't supposed to be on the net. So I have denied them access. But one lady has a Safaricom modem and she is browsing. I have disabled the DHCP clinet service, as well as the RasMan service, but somehow the modem still works. I do not have one myself to use in auditing the connection process, so I'd like to request the list/skunkters for advise on how I can effectively cripple these troublesome gizmos. My apologies to Safaricom (and prolly Zain and Orange listers) for denying you biashara :-( Thanks. Me.