If they have drilled into the slab and ripped a hole in your ceiling they are doing unauthorised works affecting common property and must stop immediately.
I suggest you contact the strata manager and tell him/her, and that you insist they be told they must cease. If you get no joy, contact Fair Trading about getting an urgent order.
http://www.ncat.nsw.gov.au/Documents/ccd_form_strata_interim_orders_application.pdf