Unlimited Plus Plan Cancelled Without My Permission

I've been trying to get my phone service plan restored since I found out it had been changed without my authorization or notification of any changes to my account. The AT&T rep I spoke with said it might have been Brightspeed, the company who took over local service in southeast Alabama from CenturyLink. He said I needed to speak with Brightspeed about what was done without my authorization, and I have been getting nowhere since June 2023, when I first discovered the unauthorized switch. Why wasn't I notified BEFORE changes were made? Before AT&T made the change, why wasn't I notified for authorization? No one would choose to change from the cheaper unlimited plan rate to "per call" charges based on minutes used.

Now I'm being charged 42 cents per minute for all direct dialed calls and other fees for service I didn't request, while I'm being shuffled back and forth between Brightspeed and AT&T reps to sort out who is to blame for the change and whether or how it can be changed back. In the meantime, my bills have more than doubled, my AT&T account shows no services, and after 3 months, I still don't know what my options are for changing back to my original unlimited plan.