REFUND REQUESTED BUT NO ANSWER

My friend and I booked a holiday package to Thailand in 2019 for 2020. Due to Covid19 we were unable to go and were informed that they do not refund but give credit vouchers. Now our problem is, we are unable to get hold of anyone from STA travel. I have sent numerous emails and have tried calling them because we want our money back due to the Covid pandemic not subsiding and I do not want to take any chances with my health because I am a chronic diabetic. All we basically want is our deposit back. The bookings were done for CHANTAL I SMITH ID *** AND TANIA LOMBARD.