I think it was possible to ring somebody from, say 021 530 xxxx to any other 021 530 xxxx number directly if you were on the same exchange or latter part, but you couldn't call 021 705 xxxx from an 021 530 number, you'd need to dial the full number. I may be wrong on that and confusing it with the more simple 0xxx xxxxxx setup which I know you could just dial the 5/6 digit number direct.
Within the major cities using the 01, 021, 031 etc area codes, you would always dial the last 7 digits if you were within that area, you couldn't just dial the last 4 digits, even if you were on the same exchange.
(EDIT - I stand corrected, see below)
However, I recall that we always answered the phone with a greeting which only included the last 4 digits.
I remember that I found it odd when we moved out of the 061 area and had to say a 5 digit (later 6 digit) number.
I do remember that we also had "local codes", which often began with a 9 rather than a 0. They were confusing times.
EDIT:
Here is a list of
local codes I managed to find. It also states that if you're on the same exchange, you just need to dial the number.
Last edited by Stuart on 3 October 2017 5:32pm - 5 times in total