Hopefully they will see this & feel very ashamed of theirselves & not only pay you but also apologize. I deal with this in my business, (hair stylist) it is very irritating.. I've had them come in & say oh I forgot my billfold/wallet AFTER I'm done (one lady did this to me 4 times in a row) it's took me a month & LONGER b/f to get my money & there are some that never came back to pay (mostly college students) & what's bad is when you see them they know they're guilty & won't even look you in the eye. guess I needed to vent!
Take a deep breath & say GOOD RIDDANCE!!