How to show different text in plot annotation without overlapping for difference choice from pop up menu?

I want to show different equation in the GUI plot for different choice from another pop up menu. However, the message from different choices overlapped when I click for different choice. What command should I look into in order to avoid overlapping messages?

My command is as below:

syms x y a b c

switch quadric_choice

    case 1
        D = msgbox('Please choose one quadric surface.');

    case 2
        axes(handles.axes4);
        D ='$\frac{x^2}{a^2}$ + $\frac{y^2}{b^2}$ + $\frac{z^2}{c^2}$ = 1';
        annotation(gcf,'textbox',[0.03,0.81,0.1,0.1],'string',D,'interpreter','latex','FontSize',20,'FitBoxToText','on');

   case 3
        axes(handles.axes4);
        D = '$\frac{x^2}{a^2} + \frac{y^2}{b^2} - \frac{z^2}{c^2} = 1$';
        annotation(gcf,'textbox',[0.03,0.81,0.1,0.1],'string',D,'interpreter','latex','FontSize',20,'FitBoxToText','on');

end