Neighbor Constantly Complaining about Heat

My partner and I live in Chicago in a 3 flat apartment building with a garden unit. The building was built around 1906 and uses steam radiators for heat. We live on the top floor which used to be occupied by our landlord, and so our unit contains the thermostat that controls the heat for the entire building.

We have lived here for 5 years (in Chicago for 14), our neighbors on the 1st floor just moved in in Sept from the PNW. Before the winter started 1st floor had some work done on their radiators to get them prepped, and now in the last month they have asked us 4 times to bump up the heat because they are cold.

We recently discovered that they went out and bought a "portable heat pump" that hooks up to the window like a portable A/C unit and according to them it blows cool air out and then sends warm air through the room. But since it hooks up to the window that means that they have an open window in an upper Midwest winter. We have also noticed that they have only complained about being cold when this thing is hooked up.

Our 2nd floor neighbor has lived in the building longer than us, and the guy in the garden unit has been around for ~3 years. Each of them have asked us to adjust the heat maybe a couple of times, but this couple moves in and it's multiple times in a month.

EDIT: We typically keep the heat set at 70-71, it's programmed to go down to 68 at night and then back up during the day.