code: public function removeNamedRange($namedRange, Worksheet $pSheet = null)
      {
          if ($pSheet === null) {
              if (isset($this->namedRanges[$namedRange])) {
                  unset($this->namedRanges[$namedRange]);
              }
          } else {
              if (isset($this->namedRanges[$pSheet->getTitle() . '!' . $namedRange])) {
                  unset($this->namedRanges[$pSheet->getTitle() . '!' . $namedRange]);
              }
          }
  
          return $this;
      }
docs: Remove named range.
  
  @param string $namedRange
  @param null|Worksheet $pSheet scope: use null for global scope
  
  @return Spreadsheet