Discovery Flight booking

I am currently on diamond level with Discovery Vitality. Last year I booked our flights to the UK to fly this year. Due to Covid and UK's still having SA on the red list I wish to change our flights to next year June. I have been trying for 2 weeks now to do so. I have sent numerous emails, I have registered with their WhatsApp communication group, I have now run out of patience as well as options to try and get through to someone. There is no number available to call to speak to someone and my emails go through daily without any appropriate response or assistance.