The WhatsApp Group chat is NOT monitored by a manager, therefore any shift issues should be directed to store in person or by phone call. The Shift Policy clearly explains how to notify the store if you are sick or have a family emergency, these procedures most be followed otherwise diciplinary action may occur.
When swapping a shift, you must consider the skill level of the other person and if they are the same 'group' of crew such as school crew or day crew. Any shift swaps are subject to store approval.