Recurring device payment after returning the device

I returned two devices to the store before my vacation in Sep 23. They still keep on charging me device payment. Contacted them 14 times regarding the same issue, each department is saying not related to them. I have no idea how the xfinity rep sent the mobile device for return as the rep asked me to send her the fedex label and which I did. Their system is not updating but the notes from the rep, she mentioned the device is returned. How do I suppose to know how the store rep return my phone? I returned 2 devices and provided 2 fedex label to the rep, I am not sure if the rep returned both devices with one label?

They did manual refund me then put the credit reversal back to my account and say it is past due!

I have filed FCC and BBB complaint. They put past due on my account for the device payment and even offering me extension, which is ridculous! The rep on phone disconnected me, hang up on me, when I asked to talk to supervisor, just disconnected me right the way.