I have only ever contacted via sms or WhatsApp, using the number on their E&B post. Add the number to your contacts, and they should appear in your WhatApp contact listing as well. They usually provide an WhatsApp update each day as to who is on that day.
Here is today's update (Becky) and as well as Luna recently.
Luna.jpg
Becky.jpg
They have generally been pretty responsive using sms.