When companies keep ignoring the NATAs over the span of many months, I enjoy fucking with the letters before sending them back. Nothing illegal, but never underestimate the power of writing not at address on a letter 100 different times. All in varying fonts and pen colours, some upside down for added effect. Maybe even some passive aggression about how incompetent they must be to not know how to update someone's address. Sprayed with a quick spritz of non flammable air freshener (I don't want to blow up a post truck, after all), and scrunched up a few times before being chucked back in the post box.

I did ask the postie about it (don't want to make his job harder), and he said as long as he can read the return address, and their robot can see the stamp, everybody finds it funny and it does a few laps of the LPO before going to the depot.