Bad attitide and lack of service

I went to Steers at the Total garadge in Kempton park. Placed an order and requested to add a milkshake. The lady said she already ordered and wont be able to add the milkshake. I asked her to cancel the order so that we can do jt from scratch and thereafter she asked me to wait on the side of the que..3 people ordered and when i asked her to take my order she refused to take my order.