you must pick a carrier code (19YY) to complete the call when using a landline; when dialing from a cell phone, if you don't use a carrier code and simply dial 00, your call will be completed by your current service provider
here are the more widely used carrier codes: Movistar - 1911, Claro - 1912, Americatel - 1977, IDT - 1914, Convergia - 1960, Nextel - 1990
Area codes & number examples
Location
Dialing format
Or using +
All areas
19YY00 1 xxx xxx xxxx
+1 xxx xxx xxxx
More info:
Area code locator - Find the area code for a US city or browse codes to see their locations