I’m working in customer service and we sometimes have people who don’t want to pay for a service we offer (fixing their stuff in IT). There are two options:
You tell me what you did when and ask nicely if we can fix it for free? You just did half of my work, of course I will make an exception for you.

You blame everything on us and want the service for free as a compensation? Bet I will invest more time to prove why it’s your fault and therefore you’ll have to pay for it.

For a plastic bag? Give it to them, it costs nothing and it’s not worth your time and effort.