I may be speaking out of turn and without all required information, but it's not unheard of for there to be a little air that makes it's way through the system after a flush/fill. Driving it and turning the wheel back & forth will usually take care of it. Definitely check the fluid level first.
With that being said, if it goes on for days & days, it's possible a suction line has an air leak and is re-introducing air into the system. If that's the case, you'll have to have them find the leak and tighten the connection or replace the hose.
2012 Frontier CC SV 4x2
Callaway Turbo Mercedes-Benz (Temporary caretaker)