When possible always use the canonical form. The more normalized the form the better. If there is a standard, use it. For this problem, let's use Google's libphonenumber, by proxy of pg-libphonenumber.

CREATE EXTENSION pg_libphonenumber;

This currently installs the phone_number type which has comparison operators and functions. It stores the number in an international canonical form. This is the best compromise in my opinion.

parse_phone_number('textnumber', 'CountryCode');

Because we can tell when phone numbers equal each other and we provide an internal normal form, we can do this..

SELECT parse_phone_number('03 7010 1234', 'AU') = parse_phone_number('(03) 7010 1234', 'AU');

(returns true). This also means that DISTINCT works so we can do this to get the effect you seem to want above.

CREATE TABLE foo AS SELECT DISTINCT parse_phone_number(ph, 'AU') FROM ( VALUES ('0370101234'), ('03 7010 1234'), ('(03) 7010 1234') ) AS t(ph); SELECT 1

That puts in..