Check whose name is on the lease - if your company signed it then they are responsible!
This was a slight bone of contention at my co between HR and expats. In the end the book was passed to us, but the agreement I signed with my co is that I am responsible for ensuring they are operational when I leave and must prove at least one full service per year.
That's all I will do. In the meantime my husband cleans the filters once a month and we will get the chaps in if we have any problems. Filter cleaning is really easy for wall mounted units - you just open the front, slide the filter out and scrub in the shower! The coils and bigger pieces of kit (located outside the apartment) only need servicing once a year.
I'd like the tel no of the co at $30 per unit please, for our annual service!