It's not limited to Nigeria, either. I experienced the same frustrating roadblocks while trying to develop websites on an East African island. (A Small Orange treated me with particular injustice based on my location and I will never get the bad taste out of my mouth when I see their name.)

However, I can't offer a better solution than taking a civil approach to vetting/rejection in case the customer is a real, innocent human being. And that doesn't seem like much of a solution.