Bad Tasting Chocolate Oatees

We bought a box of chocolate Oatees in Aug. When my kids consumed half of the box they complained that it tasted funny, not like chocolate at all, and then we found a foreign piece of cereal which was green, in the pack. I sent Pioneer Foods emails, (which contained pics of the manufacturing date, supermarket slip and the object we found) twice on the 21st, and a follow-up email on the 29th August, but I am yet to receive a personal reply from a person. Pioneer Foods have lost me as a consumer.