Even easier then!
What do you mean by ARR? I presume you’re not from UK or you’d have said STD then phone number?
No - not that I know of
Initially your number was 3 letters for the exchange followed by 4 numbers
the bit that became the STD was not something I came across as a kid but I think originally you needed to ring the operator - I remember my Dad having to do it to ring his old nurse from the spinal injuries unit during the war - they always talked on Christmas day
at some point the ARR (arrowbrook exchange) changed to 677 and 678
and at some point - whcih may have been the same - we had a 051 (later became 0151) for Liverpool (my Mum was not happy about THAT!!)
I think at that point you could also start ringing other cities without going via the operator
or at least that is what I remember
I only ever need to ring close family and later on friends - so I didn;t need or want to know much more at the time
EDIT
just to add - I was born in 1960 so became aware of phone numbers probably mid to late 60s