HPAR, one does not need to cancel their Margin account to insure shares will not be borrowed from it. One merely needs to contact their broker and let them know you do not want any of your shares loaned out. If they hem and haw about it, ask to speak with a supervisor. You have that right.
“The person who risks nothing, does nothing, has nothing, is nothing, and becomes nothing. He may avoid suffering and sorrow, but he simply cannot learn and feel and change and grow and love and live.”~Leo Buscaglia