The old you would ring the right number (5)

I believe the answer is:
three
'number' is the definition.
(three is a number)
'the old you would ring the right' is the wordplay.
I cannot really understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'right' could be 'r' (common abbreviation) and 'r' is present in the answer.
The remaining letters 'hee' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for three that I've seen before include "III" , "Snooker score for potting green ball" , "There (anag.)" , "Number that's a crowd" , "Number of Furies or Norns" .)
