Poor Service

So i went to buy breakfast and coffee at wimpy victoria centre,i was serviced by a girl named Ntedy,infront of me there was a white lady,she greeted her so nicely,kept calling her maam. Then came my turn,she didnt even greet me,the smile she had for the customer before just vanished as i approached the til,what amazed me is the fact that we seated on the couch waiting for our orders along with the white lady,Ntedy brought the white lady's order to her on the couch,opened the door for her as she was carrying her breakfast and coffee,the came my order,she just said "sorry" and from the other 2 ladies who were paying there i could tell she was talking to me,i resisted going answering her "sorry" which referred to calling,then the 2 old ladies then made me aware that this Ntedy girl was calling me,i apptoached the til,she gave me my order which was my breakfast and coffee,i opened the door for myself and then as i was going out my coffee fell... So what i want to know is,does wimpy teach their staff to only show courtesy to a certain colour of people and mistreat other races that come there to pay using the same money as the other races and even tip the very same person who treats a different race better than you... I am disgusted by Ntedy's service towards me as i witnessed a far better service before me from her to a white lady...