Atf fluid added to Lancer cvt trans. How can i fix this?

What happens if atf fluid is added to a cvt
transmission? My mechanic accidentally filled it
with 3 quarts of atf and didnt notice it for entire
day. I drained as much as i can out and replaced it
with all cvt. Now its telling me the trans fluid is
overheating and while driving the car revs all the
way to 3-4 rpms without shifting. Do I need to do a
flush? Ive also ready that light goes off when there
is too much fluid. What can i do?