You are a barista at a local coffee shop

You saw a group of six people walk in, all of them wearing dark clothes. They placed they're orders and sat down. You made they're drinks and gave them to them. A man went outside to take a call and left one of them in charge for the bill. Soon after, they got up and left. You went to get the bill but it wasn't there so you went outside and confronted them. Once he heard they didn't pay he yelled at them and gave you the money, a tip and his number