istanbul turkish lender aktif bank say thursday violate u.s. international sanction mention u.s. case regard iran sanction violations turkish gold trader reza zarrab witness testify wednesday initially handle iranian transactions aktif bank say aktif bank first hesitate open account shut account receive warn unite state transaction violate u.s. international sanction occur behalf bank lender say statement continue cooperate international national institutions result case negative impact us zarrab say use halkbank continue transactions iran aktif bank stop work halkbank executive mehmet hakan atilla defendant case atilla plead guilty aktif bank say violate u.s. international sanction