Non refundable?

I booked a flight Heathrow to Johannesburg in November 2021. The flight was then cancelled due to covid. It was almost impossible to get hold of anyone to help either on the phone or online. Finally on the third wait of over 30min I was told that I had a non refundable ticket. I have gone through all the emails they sent me and nothing even hints at non refundable. Tonight I tried to see if I could book another ticket then. This time I was helped very quickly by a very friendly and professional person. Unfortunately I can't afford to pay the difference, on top of which they have put a £460 airline penalty. Not sure what for, the agent couldn't help me with it. So now I sit out of pocket and unable to get to see my family. Not impressed at all.