I have identified the flight that I want to book - it's on Tame airlines from Sao Paulo to Lima. I found it on the site Onetravel and Tame Airline's own site has the same details and roughly the same price. But I have been unable to book the flight on Tame's website - two different credit cards were refused. And I won't use Onetravel due to the horrible reviews I've read about the site. I did a search on Expedia, Orbitz and Travelocity, but the Tame flight did not come up. I even tried Travelocity, setting my location to Ecuador.
Any suggestions other than "Use an agent"?