(CNN)"It really depends what you want. Boy? Girl? Young? Old?" The man on the phone was offering us young children with the casualness of a market trader. After a week of back and forth phone calls, his initial caginess had given way to greed. He'd heard my foreign accent and clearly decided I would pay more than the domestic rate. "We can get," he said. We'd been put in touch with the man through a contact on the ground. We were told he was one of the men running this "unofficial" displaced camp -- one of the many that has mushroomed in the town of Yola as the influx of people fleeing Boko Haram has grown beyond the capacity of the official camps. It had all been heartbreakingly simple. We'd asked who had children available to "foster" -- a catch-all code word designed to conceal the true intent of those offering up the orphaned children. The man on the phone was the end result of those inquiries. When our colleague want to see them, he was shown a group of children and asked which one he wanted to take. One, two maybe? He escaped by saying he needed to check with his "madam" -- me. I called. The man picked up and began referring to me as "sister." I told him we wanted to know what we'd need to do, if we decided we did want to "foster" the children. He told me, "Sister, Jesus will reward me," so the "fostering" was free, he said. No need for any pesky paperwork -- just a reassurance from me that the children, if I chose to take them, would "live in my heart." If I could also then find it "in my heart" to donate to those still in the camp, then that would be "God's work." In spite of the harsh measures the Nigerian government has put in place to punish human traffickers, by the government's own admission, 8 million children are currently engaged in forced labor. The Global Slavery Index says Nigeria has the highest number of people in modern slavery of any sub-Saharan country. Paradoxically, the group also rates Nigeria's anti-trafficking agency, Naptip, as one of the strongest government responses on the continent -- but it's clearly overwhelmed by the realities of working in what is now a zone of military operations, Nigeria's north. As the insecurity in the region has spiraled, the worry is that more and more children are falling through the cracks. And as Boko Haram increases its reliance on child suicide bombers, concerns are growing that orphaned children could end up in the hands of the terror group. At the camp where we finally met the man face to face, there was no attempt at subterfuge. We spoke in normal tones in full view of the children playing. I could have had one of them, I was told, but because I'd specified a younger child, they'd only identified one so far -- a 3-year-old. Did I want to consider an older girl? A 12-year-old maybe? She could look after the 3-year-old, and cook and clean. Either way, two girls would be ready tomorrow, he said. I could see them then. Our last phone conversation revolved around what an appropriate "donation" would be in exchange for the children. He couldn't, he said, bargain for it. He then proceeded to do just that, laughing down the phone at my first tentative guess of $200. Laughing again at $300. We finally found a figure he didn't find funny -- $500. I put the phone down and we traveled back to the capital that day to show Naptip what we'd found.
CNN team finds a man at "unofficial" displaced camp willing to provide children to be "fostered" He says he can't take money for them, but eventually demands $500 for two girls .