How to detected user click call or dismiss?

 

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if let url = URL(string:"tel://\(String(describing: Util.checkForNullString(contactNo)))"), UIApplication.shared.canOpenURL(url){
    if #available(iOS 10, *) {
        UIApplication.shared.open(url)
    } else {
        UIApplication.shared.openURL(url)
    }
}