"At one point i even went as far as having an automated reply of "this is not the domain you are looking for", all that did was make them double down on the attempts to send it to the wrong address"
I had a similar problem with a finance company whose fax number was the same as mine - in another area code. Complaining made it worse.
The annoying faxes on the voice line only stopped when we plugged in a fax and started faxing back applications with "REJECTED" written across them in 2-inch high letters. I'd imagine that someone started getting an earful in head office.