Am I right, you are looking for advice on how to change your
neighbour's bathroom lightswitch (presumably without their
permission)?

I would wait until they are away, then chisel out enough bricks to get
into their bathroom, then refit their pull switch with a rubber sheet
or pad between it and the ceiling to break the acoustic coupling
between it and the ceiling joists.

Getting the bricks back in place is going to be tricky, but clearly
worth the trouble....