Perhaps the answer is too late for you.
Handle(Geom_BSplineCurve) curves[4];
For each curve, you make like this:
Handle(Geom_BSplineCurve) SPL1 = GeomAPI_PointsToBSpline(pnts).Curve();
curves[j] = SPL1;
and finally you make the face:
GeomFill_BSplineCurves bsurf; bsurf=GeomFill_BSplineCurves(curves[0],curves[1],curves[2],curves[3],GeomFill_CoonsStyle);