The Web CallBack module allows you to easily add an HTML call me box to your website. Visitors simply enter their phone number in order to be connected with you or a specific destination. The Web CallBack module allows you to specify a CID to be prepended which alerts you that the call is coming from a specific callback. You can also set Dial Matches to specify which numbers users are allows to call. Once you have set your destination and saved changes you will be given HTML code to paste into your website.
Since the Web CallBack module has you insert HTML into your website that has it pull files from the module to display on your webpage, you will need to make sure your website has access to your PBX's /var/www/html/wcb.php file. This means your firewall cannot block it or any apache security such as htaccess that you may have set up. Please note PBXiaF by default blocks access to this without entering a password. You will need to modify their htaccess to allow this, and this is not something we can offer advice or support on.