I lent my quad band phone to my sister for a trip to Brazil.4 ladies in group all had phones. Only two of them could get sim cards that would work my phone was one of the ones that would not work.I have used this phone all over Europe and Middle East as well as some parts of Asia.
Any ideas why? just wondering. thanks

I would have expected your quad band to work. Brazil is on 900/1800 so a dual band will not work but a quad should have been fine.