Poor service

I had booked a flight for the 27th of November 2021 to fly back to Johannesburg to attend my nephew's baptism. The flight kept changing times to a point where I had to book another flight because I was going to be late for a meeting on that day. I had called them and they said they would give me a travelstart voucher or something like that in 6 weeks and still nothing has happened. I emailed and no reply. It's hard to trust a company that can't stick to they word. Please help me if possible