Poor customer service

I redeemed a R250 Zando voucher with my Discovery miles in June. I got an error message saying that the code cannot be used twice so I mailed Vitality about it. They issued me with a replacement code and the same thing happened. I mailed them about this on 30 June, 7 July and 13 July and they haven’t responded to any of those e-mails. Worst service ever!