I am storing a phone number in model like this:
model
phone_number = models.CharField(max_length=12)
User would enter a phone number
Others mentioned django-phonenumber-field. To get the display format how you want you need to set PHONENUMBER_DEFAULT_FORMAT setting to "E164", "INTERNATIONAL", "NATIONAL", or "RFC3966", however you want it displayed. See the GitHub source.
django-phonenumber-field
PHONENUMBER_DEFAULT_FORMAT
"E164"
"INTERNATIONAL"
"NATIONAL"
"RFC3966"