Bad customer service

Bad customer service at Jet store mams mall... Queue is always slow even though customers are few....

Today I waited for more than 20 min even thou I was the 2nd client on the queue.. I tried raising it up with the male cashier who then laughed at me, and threw my card I was using to pay at me then sang a rude song

I'm so irritated because this was not the first time it was slow or second