Being charged for device tmobile received but cannot locate

It's happening to me too. I called after many months of not paying attention to my bill and the rep over the phone during the summer told me they had the phone in the warehouse after I had returned it to the nearest UPS store. Just a few minutes ago I spoke to a supervisor about what happened and she said 2 alarming things. 1 she said whenever they say they're recording for quality and training purposes it's only at random and it's just more for training purposes because she told me they can't check the call log from the conversation I had with the rep. The rep told me they had the phone in their warehouse and they needed just to scan it in. The same thing almost happened to 2 other equipment I sent them back. They said they lost them and kept charges on my account but after I pressed t mobile to look for this stuff they finally found them. Is there any way we all can form a class action suit? Because the way it looks T mobile engaged in theft. By the way the supervisor blamed UPS and told me to speak to them and I said no because it'll all be a run around. T mobile needs to refund me and stop stealing money from my account. What they should do is take of the situation leaving the customer out of the conflict. We returned the items and we shouldn't be responsible for anything that happens in the middle of the shipping process.