- (BOOL)callPhoneNumberWithString:(NSString *)phoneNumberString {
    NSURL *url = [NSURL URLWithString:phoneNumberString];
    if ([[UIApplication sharedApplication] canOpenURL:url]) {
        [[UIApplication sharedApplication] openURL:url];
        return YES;
    }
    return NO;
}

- (IBAction)callFirst:(id)sender {
    [self callPhoneNumberWithString:@"tel:0123456789"]; 
}