High Quality Content by WIKIPEDIA articles! In many countries, mobile phones are assigned dedicated mobile phone codes within the country`s telephone numbering plan. Some countries that do not use area codes (e.g. Singapore) allocate specific number ranges to mobile phones that are easily distinguishable from landlines. One notable exception to this type of assignment is the countries within the North American Numbering Plan (the United States and its territories, Canada, and much of the Caribbean), in which mobile phones are assigned subscriber numbers within geographic area codes, and are not easily distinguishable from landlines.