Ricardo,
You would need to setup a small switch in the US, where all inbound calls (to the US and Brazil call centers) will be switched from. This switch can send calls to the US call center or Brazil call center based on certain programming like alternate call ids/call sequence, caller id/zone id, time of day and/or day of the week.
Thereafter you may send the call to Brazil over a public international call (buy minutes in bulk to get a good rate) or leae a private link to your facility in Brazil. In case of latter you would need to compress the voice bandwidth using a Multiplexer (Nortel/Cisco/Alcatel etc).
You can also leaes a public frame relay connection which works like a private link at a per call or per port charge, though I am not sure which operator provides that service between the US and Brazil.
Hope that answers a few questions. More questions? Write again..
Cheers, manoj