I am totally new to this.  And trying to get cell phone service on the
cheap.  So I am thinking about buying a phone and SIM card on ebay.  But I
am very confused by the relationship between the phone, the SIM card, and
the telephone number.  I've looked on the web but everything I have found is
either too technical or not technical enough.  Can someone recommend to me a
good online document which covers the relationship between the phone, the
SIM card, and the telephone number?

E.G. I think I've determined that the SIM card determines the phone number.
But I just talked to someone at Cingular who told me that all they need is
an IMIE# (or something like that) to assign me a phone number.

Thanks,  Bob