  Current searches for the charged Higgs at the LHC focus only on the
$\tau\nu$, $cs$, and $tb$ final states. Instead, we consider the process $pp\to
\Phi\to W^\pm H^\mp \to W^+ W^- A$ where $\Phi$ is a heavy neutral Higgs boson,
$H^\pm$ is a charged Higgs boson, and $A$ is a light Higgs boson, with mass
either below or above the $b\bar{b}$ threshold. The cross-section for this
process is typically large when kinematically open since $H^\pm \to W^\pm A$
can be the dominant decay mode of the charged Higgs. The final state we
consider has two leptons and missing energy from the doubly leptonic decay of
the $W^+ W^-$ and possibly additional jets; it is therefore constrained by
existing SM Higgs searches in the $W^+ W^-$ channel. We extract these
constraints on the cross-section for this process as a function of the masses
of the particles involved. We also apply our results specifically to a type-II
two Higgs doublet model with an extra Standard-Model-singlet and obtain new and
powerful constraints on $m_{H^\pm}$ and $\tan\beta$. We point out that a
slightly modified version of this search, with more dedicated cuts, could be
used to possibly discover the charged Higgs, either with existing data or in
the future.
