Shocking Service - Not Refunding Cancelled Flights to the US/UK

Travelstart ***. Purchased Flight Bookings to the US via the UK departing 12th December returning 28 December 2021 with American Airlines via Travelstart. Due to the travel restrictions from South Africa, we are unable to travel. We require a full refund as we have not voluntarily cancelled these flights. Travelstart have switched off their phones and are not responding clearly to our requests for clarity on the refunds. Whatsapp process is a failure and communication is unclear. American Airlines are willing to give a full refund and not sure why Travelstart are not responding.