www.webjet.com.br seems to give just one non-0800 or 0300 telephone number, (21) 3535 2525. That's for travel agencies but maybe they could direct you, if you can't find a way to call 0800 or 0300 from the U.S. Finding someone who can speak English is a different question.

p.s. I did just buy a ticket from Gol, since they're having a sale. The Web site did seem to allow one to buy using a passport # if they don't have a CPF, but I am not sure. I actually had to give up on the Web site and go through a travel agent, but you might have better luck.