In Mews when you are creating different services, you might want to also charge a price for the service itself. If you take for example Room service, usually there is 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, and remove the price of the service if needed. Navigate to Menu > Settings > Services. Find the relevant service and delete the price of it.
Don't worry, the products will still have their prices.