Charged illegally for equipment I was sent and did not ask for

I am very unhappy with customer service. I called to cancel my service almost 2 months ago. When on the phone with the agent I specifically asked if any equipment needed to be returned. I was told I needed to return my internet box and not the cables. I have been spammed about returning equipment for almost two months and kept stating I’d returned the equipment on 23 May to a specific location where I was also told I had nothing else to return. My account is showing required payment for unreturned equipment. Today I was told that the bill is for the non-returned flex box. This is the "free" flex box that was sent to me automatically-I did not request it. When I got it, I called and asked about it and was told it was included for free with my Internet service. I can't help but feel it is a scam when I am told not to return an item and then get charged for not returning said item almost 2 months later. When I just called customer service, expecting the charge to be taken off my account, I was repeatedly told that I had to return the box or pay the fee.