The HR department seemed to have some sort of dumb-fuck database that flagged me as breaching their guidelines. I got continual emails and calls from them wanting to discuss my absence. At the start I was politely telling them "No, I was in hospital for ten days with my foot pointing in the wrong direction and you have my doctors letters about that, thank you" and then after a few months I just started putting the phone down on them, and replying to the emails with "Fuck off".