Racist employee

Today I visited the Burgerking in Fairhope,Alabama. It was 1:15 central time. I pulled up to the drive thru and my family and I were treated like garbage. The lady working the drive thru was very rude and racist. She upset my son on his 8th birthday so bad he was crying.  We asked to order and she yelled I'm here very rudely. She proceeded to talk so fast we couldn't understand her. I asked her to repeat herself and she started to yell at me. I asked for a manager and she told me she was the manager and if I had a problem I could come inside and tell her to her face. I took that as a threat! She continued to scream and argue with me like a child.  I told her I would call cooperate and she laughed and told me to call them on her. All my son wanted was s milkshake! It was his birthday.  I have worked plenty of management jobs and I know that is not the way that a professional is supposed to treat customers. I'm disappointed!