Blimey, some of these replies.
OP says she followed her workplace's policy, why are people ignoring that? Not everybody has to ring up every morning they're ill. If she followed it, then she's right, her manager shouldn't be harassing her when she's ill.
And if some of you think 3 episodes of illness in a year is excessive, all I can say is that some of us have no choice in the matter. And if employers are kicking off about 3 sickness absences a year, they're shit employers. (Including yours by the sounds of it @PeachBlossom1234 - it's appalling you had to work through chemo.)
At this rate employers will be pushing people into higher rates of sickness absence, making people sicker than they already are, and eventually forcing them out of jobs altogether if they don't wake up and realise they are employing people not robots. At which point they'll be labelled scroungers for not working. Not that a bad employer would care, of course - they'd just replace them and proceed to treat the new lot just as badly, potentially impairing their health as well.
This being Mumsnet, I'm quite sure this post is going to be laughed at and I couldn't care less. Some people on here really do inhabit very narrow little worlds.