I don't know about charmed pets (haven't bothered to try) but in addition to the /pet ranged command, there is a /pet melee command, and a "pet options" menu. You access this by right-clicking on the pet itself, and there should be a pet options window which can dictate the /pet ranged or /pet melee behavior. For the necro pet at least (as well as your god pets, so that they'll PERMANENTLY hide), and I can see the same mechanic working for charmed pets, though it's possible it wouldn't.
Good luck.