Overlap CalloutMapAnnotation and other annotation

Question

I have an overlapping problem in mapkit annotation.

I set CalloutMapAnnotation in viewForAnnotation as delegate.

I have gone through multiple answers and have even tried changing z index but that too has not worked for me.

Here is an image of the problem:

I tried the following code in the method didAddAnnotationViews but that also does not work.

if([annView.annotation isKindOfClass:[CalloutMapAnnotation class]]){

     [[annView superview] sendSubviewToBack:annView];
}