To call Uruguay from Argentina, you dial the international access code 00, the country code of 598, and the eight-digit number. To make a call within Uruguay, simply dial the eight-digit number.
To call Brazil from Argentina, dial the international access code 00, the country code of 55, the area code without the initial zero, and the eight-digit local number. To call locally, dial the eight-digit number without any prefix. The area code for Foz do Iguaçu is 45.