How to close a callout for MKAnnotation in a MKMapView
In case you want to stick with the map kit documentation.
for (NSObject<MKAnnotation> *annotation in [mapView selectedAnnotations]) {
[mapView deselectAnnotation:(id <MKAnnotation>)annotation animated:NO];
}
The objects in selectedAnnotations are instances of MKAnnotation
NSArray *selectedAnnotations = mapView.selectedAnnotations;
for(id annotation in selectedAnnotations) {
[mapView deselectAnnotation:annotation animated:NO];
}