I think that constitutional requirements for warrants are discussed quite nicely in this thread.
http://www.tfproject.org/tfp/showthr...urth+amendment
Phone companies have to gather these records for billing purposes. They don't listen to calls, but they have to know who called who to be able to bill the responsible party. Those records are the private property of the phone companies, although the courts have always seen an invididual stake in that property and as such a warrant is typically required to access anyone's phone records, regardless of the level. This is well covered territory and established law.
Aceventura3, regardless of how you interpret the Constitution, the Supreme Court has actually ruled that there is a 4th Amendment right to privacy for decades.