A GSM 850/1900 phone will only in the Americas. A GSM 900/1800 phone will only work in Europe, Africa, Asia, and Brazil. A GSM 900/1900 phone will work on at least one network in most countries ...

By supporting all four bands, a quad-band phone is compatible with most GSM networks worldwide. The four bands include the 850 and 1900 MHz bands - used in the Americas - and 900 / 1800 ...