  In the present work, we investigate the decays of $B^{0}_{s} \rightarrow
\phi\pi^{+}\pi^{-}$ and $B^{0} \rightarrow \phi\pi^{+}\pi^{-}$ with the final
state interactions based on the chiral unitary approach. In the final state
interactions of the $\pi^+\pi^-$ with its coupled channels, we study the
effects of the $\eta\eta$ channel in the two-body interactions for the
reproduction of the $f_{0}(980)$ state. Our results for the $\pi^+\pi^-$
invariant mass distributions of the decay $B^{0}_{s} \rightarrow
\phi\pi^{+}\pi^{-}$ describe the experimental data up to 1 GeV well, with the
resonance contributions from the $f_{0}(980)$ and $\rho$. For the predicted
invariant mass distributions of the $B^{0} \rightarrow \phi\pi^{+}\pi^{-}$
decay, we found that the contributions from the $f_{0}(500)$ are significant
except for the ones from the $f_{0}(980)$ state. With some experimental
branching ratios as input to determine the production vertex factors, we make
some predictions for the branching ratios of the other final decay channels,
including the vector mesons, in the $B^0_{(s)}$ decays, where some of them are
consistent with the experimental ones within the uncertainties.
