I don't know about elsewhere, but in the UK it's standard practice that when you start a new job you give a contact number to your old place of work so they can recommend you.
I worked my last job as a graduate, promised if I started on the minimum wage (8.91/hr) part time, there was opportunity for me to get promoted/pay raise/ more hours. It was hard being minimum wage, especially as I was the only person in the company being paid that little.
When my review came along, my boss told me they were looking to keep me on minimum and reduce my hours. She wouldn't even concede to giving me a title only promotion. I was frustrated, but I said nothing and worked till the end of my contract and didn't renew. I legally, didnt even have to quit. My ex boss was mad, told me I could “just” work fewer hours and have the government “top up” my wages. She wanted me to believe that she genuinely thought she was doing me a favour.
3 weeks later I landed the cushiest job of my career. In my field, a boss who doesn't crack the whip, salaried and up to 8 weeks PTO yearly. For the first time I have had actual financial security. I am saving money, looking at getting out of debt and bettering my situation. I am gonna cling to this job like a koala on a tree my dudes. This, to me, is what I've been working my young adult life towards.
Today my manager showed me the reference I got from my last place of work. It portrayed me horribly. My old boss detailed that I used up all my sick days in the time I worked there. I have a chronic illness and I wouldn't go to work if I was sick. And mentioned that I took a day off (it was planned in advance) to go to a Halloween party. She basically portrayed me as a dumb, inconsistent and unreliable worker. Which is bullshit because I consistently met expectations and exceeded in every deliverable when I worked there. My sick days cant have impacted my effectiveness at the job as they are literally still using my content even now.
I was so shocked when I saw the reference. I know we didn't really part on great terms, but it was incredibly professional and I never did anything wrong. Now I just realise that my old boss was a big fish in a little pond, and she's mad that I went from being the bottom of her pecking order and in a matter of weeks, ended up somewhere bigger.