First if you ahve worldcom you cant switich to another provider.
why you may ask.
well worldcom uses a differnet system than AT&T or Sprint or even Verizon.
If worldcom does use SIM cards then it might work for the rest of the world who use GSM use SIM cards.. but then Worldcom is the only one using SIM's in the US.
Since I do not know what worldcom's network is based on I can tlak about it, but I will tell you that AT&T is on TDMA, Sprint is on CDMA 800Mhz Verizon is on CDMA 1900Mhz
By any chance did a worldcom telemarketer call.. cause they tried me to get me to switch over to them.. well I am looking for another service provider other than sprint but not worldcom.
This is a lame way to get traffic.