Phone numbers should be entered as digits, and maybe sometimes a + sign if a country code needs to be used.
A naive phone number in the United States is stored as 2025551212 and formatted as (202) 555-1212.
Internationalization of a naive phone number is achieved by adding the company naive phone number prefix to the phone number, i.e. 2025551212 becomes +12025551212.
All phone numbers can be entered either as naive or international, if the phone number is entered with the plus sign and the country code, it is stored as an international phone number.
For example, most companies in WRbil are US companies, but, for example, Airbus in Toulouse has the internal number +33561933333, and the formatted number of +33 (561) 933-333
If the WRbil company were French, with a company naive phone number prefix of +33, the phone number could be entered as 561933333 which would be formatted as (561) 933-333