The sentiment of "it's not my job"

Does something have to be assigned to you for you to be obliged to do it?

 This comes from a recent experience I had at my job. Like most bakeries, the one I work at is divided into three sections: baking, decorating, and service (starting from the back of the kitchen to the front). Apparently, there has been some drama relating to the phone. That being, no one wants to pick it up.

I get it, really. I hate talking on the phone. Moreso, I hate being interrupted to go have what is usually a 30 second conversation with a person who has less-than-stellar audio quality.

 The front was busy. The back was busy. The phone was ringing, again. This, apparently, was too much for a decorator to handle, which resulted in her yelling, "Service! Someone get the damn phone!" while being a mere three feet away from said phone. Really, that's all she had to do: take two steps and you're at the phone.

"Why don't you do it? You're right there?" A service-person asked.

"It's not my job!" She countered, and walked away from the phone. Still ringing.

So, that's it, then? It's not your job? Something was bothering you enough to yell, extremely rudely, to someone who was just asking you to do something of minor inconvenience which would relieve your annoyance.

I find this sentiment is very common, unfortunately. I get it- if I'm not being paid fairly, I'm not stepping in line to volunteer myself for extra work. I don't work hard for a corporation, I work hard for those around me: for my supervisors and coworkers who have shown me kindness and respect. I work hard to make their days and workloads easier as a way of reciprocating that respect. But the phone is closest to the decorators who get paid much more than the service workers.

I hold a sentiment of, "If you're not willing to do something about it, then you shouldn't be complaining" (notice that I say willing instead of able to). This is a prime example. If you weren't willing to help out at a very busy time with a small task, then you don't have the right to yell angrily at an innocent coworker.

 After all, is that all that dictates how much you're willing to help? If it's "your job" or not? You can't be bothered to extend even an inch of kindness to a fellow stressed coworker because the words "answering the phone" weren't printed out on your job description?

I guess what I'm trying to say is pick up the damn phone.