Askinf for a tip on top of a tip

Around 14 of us went for breakfast at Bertha's. All our coffee's were cold when they arrived at our table and it seemed a huge effort for the waiter to rewarm for us. The bill came and due to the number of persons at our table there was an automatic Gratuity Charge added to the bill. However when the waiter brought the card machine to our table and we gave him our card he also said to us " and add a tip". When we pointed our to him that there is an automatically added Gratuity he mumbled something and stormed off. Staff needed to be taught not to ask for a tip on top of a tip.