Even when S.A.F.E. has obviously lied, LTI doesn't call their bluff. In my experience, companies are slow to pay their bills for three reasons. A. Human error or sloppy payment procedures. A simple follow-up call makes your invoice a priority. B. They have cash flow problems, and they're buying time from you to pay more critical services that keep them in business day to day.
Next priority are suppliers who are most proactive in requesting payment.
It's the squeaky wheel syndrome. So be sure to squeak. They are unethical and, frankly, trying to rip you off. These businesses have no intention of paying unless you dramatically cut the invoice or take them to court. Waiting too long to call a collection agency.