numerical integration with variable limits for exponential matrix

I am trying to find integration with variable limits and then try to plot, but i am keep on getting error

A->3x3 matrix, u->3x1 matrix
syms t tau
f=expm(A*t)*int(expm(-A*tau)*u,[0 t]);
range=1e-9:1e-9:500e-9;
ezplot(f(2),range)

in this code i am keep on getting integration issue, how it can be solve?