code: public function getProperties($billingAccount)
      {
          if (!$billingAccount)
              throw new BadMethodCallException('Parameter $billingAccount is missing.');
          try {
              $r = $this->get('telephony/' . $billingAccount)->send();
          } catch (\Exception $e) {
              throw new TelephonyException($e->getMessage(), $e->getCode(), $e);
          }
          return $r->getBody(true);
      }
docs: Get Telphony properties
  
  @param string $billingAccount
  @return string Json
  @throws Exception\TelephonyException
  @throws BadMethodCallException