Banning Work Group Chats For Servers At A Restaurant? Threatening To Fire As Well.

I work at a restaurant in northern Florida. We have a group chat between some of our servers on our own personal devices. We do talk about current issues at our restaurant, or about some drama that occurs like shutting down from health inspections or how much rotation there is in our staffing. However, this group chat is about 30% work related. The rest is planning hang outs, giving rides, etc anything and everything! We added a coworker to it and when she was reading the group chat at work, our manager took her phone and went through our chat, screenshotted it and sent it to her phone. She stated that she took the phone without the employee’s knowledge. The employee says she was willing to show her however because she “has nothing to hide” The last week or so we have been told if we create any group chats between any employees we will be fired. We have been verbally harassed and accused of stuff we never said. For example, one now ex employee stated something rude about the manager. The manager now accuses all of us verbally at work , cursing and lashing out every hour or so since this happened. Is this work harassment? This is just the past week. More things have happened in my 3 months there