Business overcharged for phone calls

In this artical I read it explains how telecom is producing faulty bills to companies. 80 percent of companies are over charged due to billing errors and telecom is reaping the benifits. Companies do not take as much time that is nesseccary to look for mistakes on their bills. Is the faulty bills done on purpose? That can not be proven, but it I had to guess I am sure the mistakes are overcharges not undercharges.