Part-time employer cut down my hours to force me to quit after I found a full-time job, looking for solutions other than quitting and being passive

After graduating from university recently I was able to find a full time job. I was transparent and let my pt employer know that I could work once a week even when I start ft and they seemed okay with it. A few days before I started working ft my employer sent me a message saying not to come in as they were busy figuring out staff scheduling.

I'm pretty sure the reason for this is because my employer feels betrayed that I'm dedicating most of my time to my new job as I used to work around 3 days a week but now can only work once a week. The funny thing is that there are other staff who are in a much junior position who only work once a week with much fewer responsibilities than me so it seems that they are targeting me in particular since they can't handle the fact that I've moved on in my career. There have been several instances where I've suspected that my employer has tried to prevent me from leaving by giving negative references during reference checks for potential employers.

Is there anything I can do in this situation other than quit? I want to be able to find a way to make the best out of this situation even if it involves petty methods.

I'm very competent in my job tasks and have no issue with other staff members or people involved so I'm pretty sure my work ethic isn't in the wrong.

I live in Canada (BC) if that helps. Also changed pronouns of employer to "they" so there's only one employer if that makes it more clear.

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