When phoning internationally, the use of country codes is required. To place phone calls internationally from a mobile phone simply dial the “+” sign, followed by the country code, city code and local phone number. If you plan to use a number often, save it into your list of contacts including the “+” sign, saving time and hassle the next time.
If dialing from a landline you must use the International Direct Dialing (IDD) number and the respective Country Code.
Phoning to US with a mobile: +1 555 555 5555
Phoning to US with a landline: 001 555 555 5555
Phoning to Spain with a mobile: +34 555 55 55 55
Phoning to Spain with a landline: 011 34 555 55 55 55
Example of use: When in, say, Europe and using a mobile phone with a north American service provider, dial as if you are phoning from North America. Example: When calling on an AT&T (for example) phone brought from the US and calling a number in Burgos from your hostel in Pamplona, first dial +34, then the number provided. Most businesses along the Camino list the +34 with their numbers.