Polyatomic Reaction Charges
When a Calcium atom loses two electrons, it attains the stable electronic configuration of the noble gas Argon. Thus, Calcium cannot have a $\ce{+3}$ charge in any ionic compound. So, the ions forming your salt are $\ce{Ca^2+}$ and $\ce{PO4^3-}$. We need to balance the charges to obtain a neutral salt. We can see that the least common multiple of the charges (2 and 3) is 6. A total charge of $\ce{+6}$ can be obtained by taking three Calcium cations, and this can be balanced by taking 2 Phosphate anions.

Calcium Phosphate is $\ce{Ca3(PO4)2}$