Huletts aftercare service failure

I bought two bags os sugar about two months ago and found large discoloured granules in both bags. I made a video recording while removing the pieced and forwarded it to Huletts. The rep told me that Hullets will send me a voucher for the spoiled products. She gave me a tracking number for the voucher. I reported the her that the tracker did nit work. She suggested I call the post office to find out where the voucher is. I dont understand that reasoning. Huletts failed to deliver on their part.