Ideally you should have a perfect grid and them you can do this kind of plot. In your case, however, you have only scattered values and some grid points are outside your domain, which means that to plot the whole domain you would have to extrapolate the data and even get very wrong results.
A better solution is to interpolate only between the points you have and then plot the result. You can do this by first triangulating the points and the use the trisurf function to do the plot. An example code can be seen below:
A = xlsread('LMS.xlsx');
T = delaunay(A(:,1),A(:,2)); % Triangulation
trisurf(T,A(:,1),A(:,2),A(:,3))
xlabel('x')
ylabel('y')
colorbar
shading interp
view(2)
