Thanks. I have found a way to do that. I have added table in plot code..
Table[ParametricPlot3D[
Evaluate[Table[{i*h, t,
First[Subscript[u, i][t] /. lines /. A]}, {i, 0, n}]], {t, 0,
1000}, PlotRange -> All,
AxesLabel -> {"Spatial(x)", "Time(t)", "Height(h)"},
BoxRatios -> {6, 6, 6},
PlotStyle -> Directive[Magenta, Opacity[0.25]], ViewAngle -> All,
Boxed -> False, ImageSize -> Medium], {A, 10, 6000, 3000}]
This way, I did not define A at the beginning and assigne the A value in plot.. It is for 3 A value but one reduce the step size to get more A value graph..