showing favoritism

I went in the service station to grab a bite so i made an order puff pastry and soda i was handed a slip for the puff pastry and told to go pay first and when i went to the pick and pay till to pay i saw that everyone else had their item's in their hands while paying for them so i asked why Em i treated differently the manager said i didn't see well i responded saying 4 more clients where handed their goods in front of me but I was given a slip to PAY AND THE manager said she will investigate so as I was leaving the manager said she is tired of people like me.