A method for monitoring traffic revenue flows for a plurality of communications companies using Information Technology (IT) systems, including the following steps (v) designing an optimal sample of transactions that maximizes the probability of detecting billing errors done by the communications companies; (vi) executing transactions from the optimal sample of transactions through a plurality of communications networks and recording test transactions data ,using concurrently a shared infrastructure comprising a plurality of robots for generating the transactions; (vii) collecting invoice lines from the IT systems in a non intrusive way, through an automated browsing of the web sites of the communications companies; so as to extract billing data for each test transaction, and (viii) processing the recorded test transactions data so as to re-rate billing for the test transactions, and matching said re-rated transaction billing data to billing data invoice extracted from the collected invoice lines, so as detect billing errors.