When a client turns on you when it's time to pay... 😑

That's actually very sad.. I have been in these situations while doing freelancing. Now I take advance payment.

That happened to a friend a while back. First the client delayed payment because the program was "unusable". Then they asked for an update and my friend obliged, but used it as an opportunity to time bomb the program.

The client persisted that they couldn't use the program, so they shouldn't pay. My friend eagerly awaited the day when the time bomb disabled it, and of course some woman working with his program immediately called and told him:
-Help! Your program stopped working, and we absolutely depend on it!
-Oh? That's funny, because your boss told me that you couldn't use it...

The client payed within hours.

@Grumpy I would have loved to be a fly on the wall on the client end.