Can we add a pop up to mobile Joomla

I was wondering is Mobile Joomla had an option to introduce a pop up. Clients when they get on a site have a hard time read and navigate to the site. We are a helpline so I wanted to put a screen that will show that they can text us or call us toll free. Also an option to just close that window.

You can add a javascript like

if(document.cookie.indexOf("first_time_visitor=1")<0){

  var exdate=new Date();

  exdate.setDate(exdate.getDate()+10000);

  document.cookie="first_time_visitor=1; expires="+exdate.toUTCString();



  alert("Some text to display");

}

to mobile template (actually it's better to make it to be custom html module, because of templates are overwritten at update).