public function getCreditLeft()
    {
        $this->checkCredentialManagementRights();

        $credential = $this->getSMSAPICredential();
        $SMSProvider = SMSProvider::factory($credential[MobileMessaging::PROVIDER_OPTION]);
        return $SMSProvider->getCreditLeft(
            $credential[MobileMessaging::API_KEY_OPTION]
        );
    }