You are right. It isn't cool. But I assert that the not cool party is the employer who sprung an on call job requirement without any warning.
Additionally, if this job duty was actually important, then the employer would actually react with some criticism when they discovered that an employee was not performing this duty adequately. The fact that the employer isn't upset about having the on call employee ignoring messages means that it isn't important. Making employees being on call when the employer doesn't actually care about anyone being on call is also not cool.
Additionally, if this job duty was actually important, then the employer would actually react with some criticism when they discovered that an employee was not performing this duty adequately. The fact that the employer isn't upset about having the on call employee ignoring messages means that it isn't important. Making employees being on call when the employer doesn't actually care about anyone being on call is also not cool.