Please help, job at risk and need advise!

Ok, let me start of by telling you a policy my work has and I didn't know about it. They don't allow you to be on your cellphone in the warehouse at all, on the clock or off the clock. I was waiting to clock in a little over a month ago, and was making sure my phone was on silent, when my boss came over and asked what I was doing. I just told him," turning my phone off". He responded," you weren't just on your phone were you?" I said," Oh I haven't clocked in yet sir, just turning it off." He said"you know you are not allowed to be on your phone at all, company rule is to not be on cellphone in building, even if off the clock." I told him I was sorry and I didn't realize it was company policy. Later that day I was surprised to receive a write up for the incident that happened earlier.

I am currently a MHOC(Merchandise handler on call) I get 40 hours a week, so pretty much a full timer. Just without benefits. For about two years now.

My job is starting to hire for fulltime, where I will get benefits and payed time off, my boss pulled me to the side after announcing this to everyone and told me that I would not receive a full time job because I had the cell phone violation, and instead I was going to be moved to part time. And there would no longer be a MHOC title. So basically, because I had my phone out before clocking into work, and getting into trouble for it, I am being forced into a 24 hour weekly job, down from my 40 hour job. Can I do anything about this? If I was forced into this job, is there any way to get money from unemployment or anything like that?(A fulltime associate told me yesterday that she was hired on with a write up over her attendance, and phone. But they still hired her.)

By the way, I went to human resources last year over my clerical cheating. I was the only one to report it, and I am the only one not being offered a fulltime job.

Any help on this would be amazing, or suggestions. I can't live off of a 24 hour job, and I don't want to start over again as a seasonal or MHOC somewhere else. Jobs are hard to come by without prior experience, or college education.

I live in Tennessee

Thank you so so much for taking the time to read this long question, I just wanted to make sure to give as much info as possible.