code: func (m *Monitor) VerifyBillingLags() error {
  	// Checking billing lags.
  	// All channels, that are not suspended and are not terminated,
  	// but are suffering from the billing lags - must be suspended.
  	query := `
                SELECT channels.id :: text
  		FROM channels
                       LEFT JOIN sessions ses
                       ON channels.id = ses.channel
  
                       LEFT JOIN offerings offer
                       ON channels.offering = offer.id
  
                       INNER JOIN accounts acc
                       ON channels.agent = acc.eth_addr
                 WHERE channels.service_status IN ('pending', 'active')
                       AND channels.channel_status NOT IN ('pending')
                       AND acc.in_use
                 GROUP BY channels.id, offer.billing_interval,
                       offer.setup_price, offer.unit_price,
                       offer.max_billing_unit_lag
                HAVING COALESCE(SUM(ses.units_used), 0) /
  	      offer.billing_interval - (channels.receipt_balance - offer.setup_price ) /
  	      offer.unit_price > offer.max_billing_unit_lag;`
  
  	return m.processEachChannel(query, m.suspendService)
  }
docs: // VerifyBillingLags checks all active channels for billing lags,
  // and schedules suspending of those, who are suffering from billing lags.