So you’re doing more work for the same pay? If it’s not in the job description/contract, then they can fuck off.
Every (US) job description I’ve had save one had a line to the effect of “… and other duties as required by management.” Not to follow would be considered insubordination and could lead to termination with cause. Job description in this case is just a broad-stroke outline of what the job is supposed to entail.
The “save one” was a job with a strong union presence. In that case, going outside my job description could lead to me and my manager being in trouble.
I once worked a call centre during late shift and my manager asked us to clean the bathrooms. I told him they can hire a janitor because I won’t be cleaning anything since I wasn’t hired to clean. Didn’t have to clean the bathrooms. Sometimes standing up for yourself works
Depends on the job, and how good your read is of the situation. My experience has been that managers guilt trip or do other emotional games when they’re out of other options. In that case, it may be a safe bet to stand up to them.
Other places you’re more replaceable, or the manager doesn’t care and has an axe to grind. Then it’s trickier.
