If the web page a contains phone number you can make a call using your phone's dialer. This code checks for the url which starts with tel: then make an intent to open dialer and you can make a call to the clicked phone number:
public boolean shouldOverrideUrlLoading(WebView view, String url) {
if (url.startsWith("tel:")) {
Intent intent = new Intent(Intent.ACTION_DIAL,
Uri.parse(url));
startActivity(intent);
}else if(url.startsWith("http:") || url.startsWith("https:")) {
view.loadUrl(url);
}
return true;
}