At GRU Airport´s terminals you will find agencies of the main banks in the country.
Here is a list with the location and working hours of each bank:
BANCO DO BRASIL
Terminal 2 -
Mezzanine –
Check-in B
+55 (11) 2445-4960/4962
10:00 am - 7:00 pm.
http://www.bb.com.br
BANCO 24 HORAS
Atms
Terminal 2 - East and West
Terminal 3 - Mezzanine and Boarding
24h
DAI ATM 
Atms
Terminal 2 - Public Area: Check-in D
Restricted Area: West and East Boarding, East Landing
Terminal 3 - Disembarkation and Mezzanine
24h
LOTÉRICA - LOTERIAS DA CAIXA
Terminal 2 - Check-in D
(11) 2445-2547
9h - 19h