Still waiting for Healthy Food cashback 3 months later - appalling customer service

Discovery messed up my Healthy Food calculation for August and admitted there had been an error. 3 months later and I am still waiting! I had been told the money would be paid on 31 October, but that date came and went without a peep from Discovery. And when I try to get hold of them they don't respond - I e-mailed 2 weeks ago and have followed up twice but all I get is a response saying they have received my mail. Discovery's administration and customer service is appalling.