Du'a using Allah's Name Al-Wakeel

اللَّهُمَّ يَا وَكِيلُ تَوَكَّلْنَا عَلَيْكَ فَاكْفِنَا

Allahumma ya Wakeelu tawakkalna 'alayka fakfina

O Allah, The Trustee, we rely on You, so suffice us.

A general supplication, not a narration from the Prophet (peace be upon him).