When you are creating different services in Mews, you might also want to charge a price for the service itself. With Room service, for example, there is usually a service fee charged for every delivery on top of the price of the products ordered.
If you notice that there is a service fee added whenever you post a product, check the setup of your services. Remove the price of the service if needed. Navigate to Menu > Settings > Services. Find the relevant service and delete its price. Don't worry, the products will still have their prices.