An Office Assistant's responsibilities include taking calls from customers and delivering messages while also using basic office equipment like faxes or scanners. They help maintain files to keep track of important documents, organize travel arrangements, manage supply inventory and perform data entry as required. An Office Assistant's responsibilities include taking calls from customers and delivering messages while also using basic office equipment like faxes or scanners. They help maintain files to keep track of important documents, organize travel arrangements, manage supply inventory and perform data entry as required.