Look into my....eye....

Picture it.  I was in an apartment feeding cats.  It is very nice building on a very nice block with about 6 units in it.  I bent down for a cat head scratch (her head, not mine) and there is a very sturdy knock at the door - slightly less aggressive than a police officer.  I am confused as I was on the 2nd floor of a locked building.  I opened the door only to find an older gentleman with greasy white hair, greasy leathery skin, 1 good eye and 1 white eye, and he was wearing dirty jeans and a dirty flannel.

He said, "I need to come in and change the air filter!"    I was taken aback because I was not expecting anyone to just show up, let alone to maintenance. I told him that this was not my apartment, I was just cat sitting and that no one told me that this was ok.  He repeated, "I need to change the air filters, it will just be a minute."  And again, told him that I need to talk to my client, I'm not ok with just letting them in.  Then another guy yells from upstairs, "It will just take a minute to change the filters, we will be right down."  I shut the door, call the client, she didn't pick up, and then a minute later they just come in stating that it will take a minute. I kept saying that I understand that, but I don't have the authority to just let people in.  It's not my apartment.  They basically brushed by me with a ladder and changed the filters and walked out.  Got a hold of the client later and luckily she was ok with it (happy that I happen to have been there for this fiasco).  But seriously, any other place that I have been where someone was there to do work and I was unaware of it, they understood why I wouldn't let them in.  These guys couldn't care less.