Mate take your guys out of phalanx mode, run them up close to your opposition and then put them back into phalanx.

Its also best if you do it as a whole line, for instance sending just one phalanx into an enemies lines isn't very bright, better to send a whole line of six or more with no gaps between them ploughing into the enemy battle line.

The AI at the momemnt isn't very smart and it has no idea how to deal with phalanxes.