Faulty product/batch

I recently informed Danone about a faulty product that I bought. I was contacted and asked to provide batch numbers and all relevant info. This was on the 6th of January. Danone said that they would provide me with a voucher but have not heard anything since. I would expect better service,since I most probably helped Danone identify a faulty batch of products and thus avoiding further customer issues. This is poor customer relations!