You've probably noticed that many international phone numbers begin with a plus sign. Here's an example: +44 700 000 0000. Some of you may know that 44 is UK's country code, but what does the plus sign in front of the country code mean?
The sequence required to dial a foreign number is: International prefix - Country code - National subscriber number. The plus sign before the country code means "add the international prefix" of the country you are dialing from. So, using the example above, if you were dialing from the US you would replace the plus sign with 011, while, if dialing from one of the numerous countries using international prefix 00, you would instead have 00 44 700 000 0000.
Here's an international prefix list.
These days you can simply enter the plus sign before the country code. Cell phone devices allow it and wireless networks automatically acknowledge the international call. In this case you no longer have to enter the international prefix.
The big advantage using the plus sign is that you don't need a different international prefix for each country you are dialing from. Therefore, saving numbers in your cell phone memory using the +xx... international dialing format is usually a good idea. Domestic calls should also connect when dialing in this way from a cell phone or Voice over IP set.
Long pressing 0 (zero) will dial + (plus) on most wireless devices.
If you see an international number that has a plus sign before the country code you either dial + or replace it with your country's international prefix.