From page 219 of the Monster Manual:
"A remove disease or heal spell cast by a cleric of at least 12th level also cures the affliction, provided the character receives the spell within three days of the lyconthrope's attack."
After the thrid day, only remove curse or break enchantment will work, and only during the three days of a full moon, and a will save is still required.
Also, this only affects afflicted lycanthropes, not born ones.
Anyhow, if it wasn't the first three days, the DM fudged it (Rule #1: The DM can't cheat if he makes the rules). The section is actually pretty long and involved so pick up the MM and look at the lycanthropic template.