I actually found a jazz/hip hop/k-pop dance studio by Dongnae station.  What kind of dance are you looking for?  They teach only in Korean, but the teachers are really nice and it doesn't bother me at all.  If you get off at Dongnae Station, take Exit 2 and make a right out of the exit.  Then turn left at the first major street and walk straight.  You'll pass a Mega Mart on your left- when you have reached the crosswalk directly in front of Mega Mart, make a slight left down a smaller road.  Once you reach the dead end, turn left and it's the second building on the left, 5th floor.  Kim Eun Joo Jazz Dance Academy.