Flight Centre don't want to help after paying them

I bought flight tickets (British Airways) to go to England in May 2020 through Flight Centre.

When I purchased the tickets (December 2019) the agent advised us to take a full circle ticket meaning we take an Kulula (Part of British Airways) flight from my town to Johannesburg and from there on an British Airways flight to Heathrow, London.

On 27/03/2020 I received an email from British Airways stating I should request an voucher which is valid for 12 months as we will not be able to travel to our destination in May 2020.

So, after trying to claim the voucher on my side, British Airways informed me via email that since we used an travel agent (Flight Centre) they must submit the request.

I then proceeded to contact Flight Centre and informed them about the situation. My agent then came back to me a day later stating that we are not eligible for a voucher because we included Kulula flights with our purchase...

Flight Centre's agent said there is nothing they can do as they are just the "middle man" in the transaction... At first the agent did answer my calls on his mobile number which is displayed on his email signature etc. Now when I try to contact him he just ignores my calls.

I paid Flight Centre to be my middle man, I paid Flight Centre to ensure I arrange my Travel Arrangements in the correct manner and now when I need them the most they ignore me...

I am shocked and disgusted that they were happy to take my money and now don't want to give me back my money for a service they cannot provide.