RatePlan.fetchUnbilledRatedUnitsTotal

// For a specific product on a specific AutoBill
// fetch the array of ratedUnitSummary objects
// for all RatePlans within a specific date range.

$rateplan = new RatePlan;
$response = $rateplan->fetchUnbilledRatedUnitsTotal(
   null, # account
   $myAutoBill, #
   $myProduct, #
   null, # ratePlan
   '2012-03-01', # start
   '2012-03-31', # end
   0, # page
   50, # pageSize
);
if ($response['returnCode'] == 200) {
   $summaries = $response->['data']->ratedUnitSummary;
   foreach ($summaries as $sum) {
      print $sum->ratedUnitTotal;
      print $sum->currentTotalRatedUnitsBill;
   }
}