No matter the details, your story is common. You got on the wrong foot fast and remained there. You were played when told that you were passing at the end. That added to the shock factor when the rug was pulled out from under your feet. Even if you should prevail in this situation, your tenure at this school is not going to be pleasant for however long you last. You might be better off in trying to find a new school home.
You walked into a situation with your phone that was preventable. Many people despise the use of cell phones in the school setting, on the job, and in other places. Having a cell phone in one's hand can send off a bad vibe, especially to someone who is looking for ammunition. In the future, it might be wise to leave you phone in the car, or totally turned off, in your purse. That way you have eliminated the phone from causing problems for you.
It could be said that it is common sense to report problem situations, no matter how slight, to the instructor. But yes, this should have been communicated to the group on day one. Yet, once you realized you were in the hot seat, you should have become proactive in covering your back for any and every little thing that might be used against you.
Your witness was spot on in his assessment that you have been targeted. You will remain targeted for your tenure at this school. You need to make a drastic change in your outlook and your behavior if you intend to succeed there. As previously said, you might find it easier and less stressful to start over elsewhere. Good luck.