Zero response from useless customer service staff

I was given a 20% off voucher as compensation for having been sent a damaged product. This was sent to me in May 2017. I was travelling for a few months and thus decided to try and use the voucher in September, only to see that it had expired. After enquiring as to why this was, I was told by Zizo George that the voucher had expired in July, because it was issued in March. How could it have been issued in March when I only got it in May? And why wasn't I advised that the voucher would expire? Absolutely pathetic service. I was told "I hope this is in order". Thereafter I continued to try and contact someone for a response but of course zero replies from anyone. It seems that they just give up when there is something they don't want to fix even though I did absolutely nothing wrong. PATHETIC!