When you buy food you have a contract with the seller in the supermarket or restaurant, for example. You should therefore, first complain to the manager or person in charge of the establishment where you bought the food. If you can, make your complaint in person. Clearly state your problem and how you would like it to be solved. Never lose your temper or abuse the person dealing with your complaint. Keep a record of your action - details of conversations, the name of the person to whom you spoke and the agreed outcome. Always follow up your complaint with a letter (keep a copy), even if it has been resolved to your satisfaction.