Bought two coffees at the hotel lobby. The coffee ...

Bought two coffees at the hotel lobby. The coffee was about 7USD each, much more expensive than Starbucks. Paid by cash and they came back with half of the change. I asked the waiter where is the rest of my change. He came back again with less than full change. I seriously think this hotel is just shady. Should have stayed at the next door JW. You need to wait for guest to leave the tip. You can t just assume you can take half of the change as your tip without checking with customer.