Danone ultra mel

I purchased an Ultra Mel 1lt custard from pick n pay yesterday, 26 dec 2018. On opening the product at home, an odour was immediately released from the packaging and on tasting it, it had a chemical kind of taste. I contacted danone offices this morning, 27 dec, there only response is an apology and to post me a formal apology along with a voucher. With the state of our postal services in south africa i will receive it after 6months if at all. I asked for it to be emailed rather, they don't do emails on snail mail. Besides the point, if i just want the product replaced i would gladly return it to my pick n pay for another 1 or a refund, no questions asked. They would've taken me more seriously than the actual manufacturers of the product. My concern is that the taste is not even that the product is expired, because the date is only next year february, but my concern is the pungent chemical smell and taste from the product, and if it may be poisonous and if more than 1 box has been contaminated. I don't need a voucher or replacement, I'll get that at my pick n pay thank you, i need you to take your complaints seriously.