[1]Supplicate with certainty — the du'a of the oppressed is carried on clouds.
[2]Say: "Hasbi Allahu wa ni'm al-wakil" (Allah is sufficient for me, best disposer).
[1]The du'a of the oppressed is answered even if the oppressor is a pious person.
[M]Oppressors: beware — there is no barrier between du'a of the wronged and Allah.