Very poor service and attitude of staff

We bought from mc donanlds yesterday 3 burgers with chips. Apon arriving at home we only got 2 burgers the staff was chatting away and joking and not concentrating at the order. We pay for food not to get any. Very very disgusting will never buy any thing from them and will spread the word to friends and family. When we phoned they said come and pick up your burger???? It was not my fault so they should have offered to deliver an complete order!!!! Sis never again.