Not AMPHI
AMPNI Aegean Marine Petroleum Network Inc (ANW)
AMPNI is the Aegean Marine that Mercuria acquired, which was previously acquired from Melissanidis in 2016 by activist investors. AMPNI was sister company to Aegean Oil & Gas (still owned by Melissanidis) , so probably both run from the same offices originally. That's why Melissanidis still had tons of access, both physically and virtually, after the sale. He should not have had that access any longer, but he did. And he used it to commit the fraud and later take control of their data systems once they were onto him.
Actually I think the fraud was already underway upon sale of ANW, and the sale was part of the scheme to keep the cash while selling off fraudulent Accounts Receivables. And he used his illegal access to try and cover his trail. But it became uncovered during the audit.