I think Ag2SO4 is only partially soluble (kps=1,4*10-5 M3), so it must be difficult to do.
I´d add BaCl2, calculate SO4 (BaSO4 is insoluble), and filter the white solid.
Then (when there´s not SO4 in solution) I´d add AgNO3 and calculate Cl- (knowing the quantity of BaCl2 we have added to subtract later).