Especially to rationally allocate international telephone numbers to different lands and areas of the whole world or to mobile phone providers the telephone numbering plan is used. There’s still a distinction between dial plans and numbering plans. Or there can be a closed numbering plan existing in places like Canada or North America. For closed numbering plan it is important that there are local numbers completed with fixed length area codes.

An open numbering plan denotes that numbers and area dialling codes can vary depending on the country and region they are located in. This numbering plan is used in many countries today. Dialing the phone numbers denoted by this system you should be sure to anyway dial the digits of the subscriber’s number, remembering that the units of the calling code mustn’t be always dialed.
In spite of the attempts of the International Telecommunication Union or ITU to define the standards of numbering plans and international dialing codes they still stay different in different places. Firstly double zero was meant to serve as an international access code. Many countries have answered yes to the offer and assigned the code, still as assigning it was not mandatory for the nations in a number of them like Canada the dialling codes remained as they used to be. Missed the idea? Try brand reverse phone number!

The international numbering plan lets distribute country codes which mean the calling code for one or several countries. The E.164 standard is exactly for controlling country calling codes at the international level. It measures the standard length of a complete international telephone number. It is just supposed that the country itself defines the phone numbers on its zones. So here are the variants of regional area codes with:

- Strictly set standards of the dialling code that contains a certain number of units like three in United States or 1 in Australia and New Zealand.
- An indefinite length. That is when the number of digits changes like in Argentina (from 2 up to 5), like in Japan (from one up to five) or like in Peru and Syria (from one to 2).

- The standards of long numbers that simply include the area dialing code. They apply it e.g. in Norway. They call it a closed numbering plan. Sometimes trunk dialing codes are applied in countries like Italy, the Netherlands, South Africa or others. And usually for this destination 0 is dialed.

The calling code normally helps to define the cost of the call. It’s generally not so expensive to call on the phone numbers with the same or neighboring dialling code then on the numbers having area dialing codes of distant countries.

Still it is mainly otherwise in the USA as there the rates for home calls are defined by the state norms so the prices frequently appear to be bigger than for trunk calls.

Still there are several places in United States where area dialing codes serve for a truly large area. In this case different rates are used depending on the distance between the subscribers.

The rate centers commonly assign costs for territory sections counted in pieces of about six, 12 or more miles. However, it went the other way with the deregulation of local telephone services.

It’s now turning popular among the subscribers to take the so-called “all-you-can-eat” plan (a set price of about thirty dollars monthly as reported for this spring letting reach any place of United States).