Opodo complaint: no refund received for my cancelled flight

I booked my return flight from the Opodo website my booking details are as followOpodo booking reference: 7026165826 – Airline booking reference: PMZYER, my outward journey was on 21st March 2021, and my return flight was on 21st May 2021. My outward journey went well but my return journey has been canceled due to unknown reasons. I tried getting booked on other dates which weren’t available. so tried emailing them to book my return journey but that never has had happened .every time I received the same email asking me to call the customer care number.
my husband tried many a time to call them but he only put it on hold or received only automated answers. so I gave up and booked my return flight directly .now am back in the UK and trying to get hold but it’s been nearly 45 mint and am still waiting to be served by their customer care.
there is no option where I can initiate a cancellation or refund feeling so frustrated.
kindly help to get my refund.
Nutan Bala