Thanks Jackie,
But that's not what I wanted.
My request was to completely remove the label (flat rate in this case) and the colon (:) character, leaving in the table display only the prices :
SOUS-TOTAL 13,50 $
FRAIS DE LIVRAISON 3,00 $ (without label and colon)
TOTAL 16,50 $
Shpping price will always be 0,00$ or 3,00 $ according to order.
That's why I left flat rate field in WC empty, but still, a colon is displayed and I looked everywhere to find this character.
I suppose this is generated in the WC core files ? In that case, I won't modify that and juste use generic title for that.
Thanks