"Pull another 500mcm"? What size conduit? No easy task. Your going to have to pull all the wire out and then pull the extra wire back in. I hope you have not made any connections yet! I would get that guy's (POCO) supervisor or his supervisor and explain that it is his fault, not yours. Fight buddy. You said single phase to the POCO rep.
I don't understand how a project of this size would not have some kind of paper trail. Find the proof. He had to have made a report when he was there. Look at your records too.
