How to make a phone call in Xamarin.Forms by clicking on a label?

Xamarin Essentials PhoneDialer

public void PlacePhoneCall(string number)
    {
        try
        {
            PhoneDialer.Open(number);
        }
        catch (ArgumentNullException anEx)
        {
            // Number was null or white space
        }
        catch (FeatureNotSupportedException ex)
        {
            // Phone Dialer is not supported on this device.
        }
        catch (Exception ex)
        {
            // Other error has occurred.
        }
    }

A Label is not interactive, so you need to use a Gesture to make it respond to taps:

var tapGestureRecognizer = new TapGestureRecognizer();
tapGestureRecognizer.Tapped += (s, e) => {
    // handle the tap
};

// attache the gesture to your label
number.GestureRecognizers.Add(tapGestureRecognizer);

to make a phone call, you can either use the built in Device.OpenUri() method with a "tel:1234567890" argument, or use the Messaging plugin:

var phoneDialer = CrossMessaging.Current.PhoneDialer;
if (phoneDialer.CanMakePhoneCall) 
    phoneDialer.MakePhoneCall("+272193343499");

A quick snippet that is quick to use the phone's dialer app from Xamarin Forms:

    var CallUsLabel = new Label { Text = "Tap or click here to call" };
    CallUsLabel.GestureRecognizers.Add(new TapGestureRecognizer { Command = new Command(() => {
           // Device.OpenUri(new Uri("tel:038773729")); // Deprecated
           Launcher.OpenAsync("tel:038773729");
        }) });

Device.OpenUri() is obsolete. Use Xamarin.Essentials:

Launcher.OpenAsync("tel:" + PhoneNumber);