This attribute indicates whether or not to allow national format
E.164 addresses. If this attribute is set to a value of Yes (=1) then
national format E.164 addresses are not allowed and international
format addresses only are allowed. If this attribute is set to a value
of No (=0), then national format E.164 addresses are allowed.
If only international format E.164 addresses are allowed, then the
'e164NatlPrefixDigit' attribute is not required, nor is the
'e164IntlPrefixDigits' required.