Hi, I am looking for data on the volume of phone calls in the United
States (or a particular region of the US) at the weekly or monthly
level during some prolonged period over the last several years.  Data
on just cell phone calls, or cell phone calls of a particular carrier
(or land line calls from a particular carrier would suffice).  And the
time period should be at least a couple of years (again, monthly or
weekly data extending at least two years) anytime after 1990.  Thanks!