  We consider a model for the electroweak interactions with $SU(3)_L\otimes
U(1)_N$ gauge symmetry. We show that, it is the conservation of $F=L+B$ which
forbids massive neutrinos and the neutrinoless double beta decay,
$(\beta\beta)_{0\nu}$. Explicit and spontaneous breaking of $F$ imply that the
neutrinos have an arbitrary mass and $(\beta\beta)_{0\nu}$ proceeds also with
some contributions that do not depend explicitly on the neutrino mass.
