Why is everyone assuming this is how it works?
"A cleric who is neither good nor evil and whose deity is neither good nor evil can convert spells to either cure spells or inflict spells (player’s choice).
Once the player makes this choice, it cannot be reversed. This choice also determines whether the cleric turns or commands undead."
(
Spontaneous Casting for the Cleric)
You make the choice at character creation. It sticks with you for as long as you have class features. A spontaneous-healing (and turn undead) Cleric that turns evil still spontaneously heals and turns undead.