Light Fantastic(1964)

In this romantic drama, a plain, lonely secretary wins three dance lessons. Her handsome instructor tells her that she is quite talented and cons her into signing a long-term contract. She soon finds herself in love with him, and an affair begins. The normally cold-hearted instructor is surprised when he finds himself genuinely returning her affections. Trouble ensues when she dances with another instructor who gives her exactly the same sales pitch.