Castraphone is not a word! However...the answer is 4 pairs of letters... ST (ST) RaP (PqR) HonE (EfgH) ON (NO)
eight
i love you you love me where a happy family to all the men a woman will love youshe will come on day so dont worry
Ther are 6 letters in the word letter two of which are repeated which gives a total of four different letters.
Unique letters: 5 (L,E,T,R,S) Total letters: 7 (L,E,T,T,E,R,S)