Let $W(m, n; \underline {\psi})$ denote the set of $\psi_1,\ldots,\psi_n$-approximable points in $\mathbb{R}^{mn}$. The classical Khintchine-Groshev theorem assumes a monotonicity condition on the approximating functions $\underline\psi$. Removing monotonicity from the Khintchine-Groshev theorem is attributed to different authors for different cases of $m$ and $n$. It can not be removed for $m=n=1$ as Duffin-Shcaeffer provided the counter example. We deal with the only remaining case $m=2$ and thereby remove all unnecessary conditions from the Khintchine-Groshev theorem.