Complaint Review: Comcast

When I first signed up with Comcast which was about 4 or 5 years ago, I did rent the modem from them for a few months. But later when I asked them way to lower my monthly fee and I was told to purchase my own modem.  I then purchased the competive modem on eBay a few days after and immediately returned the rental modem to Comcast as advice.  I was told it would take a following month for the discount went into effective and since then I have not been charged for modem rental anymore.  Last week I received an email from Comcast to alert me, as usual, of the upcoming due date and I found out the fee was raised by $ 8.00 due the fact that they claimed I still have been renting their modem.  I then called comcast and talked to Linda over service cancellation department that I have been using my purchased modem for the past at least 4 years or so that was why I have not been charged for renting it, but why all of a sudden it becomes an issue. She said after a recent auditing Comcast found out that I still have their modem. and asked me to read the MAC address on my modem to see whether it does belong to Comcast or not and I did then she claimed that it was Comcast's.  She also accused me of buying a stolen unit and therefore I have to pay for additional rental charge.  In addition she follow up with an email asking me to return the item.  She even questioning me for proof of purchasing the item which I bought over 4 years ago.  However, if some legal counselors out there consider this as a good case to take then I will defenitely take my time to contact Paypal for proof of purchasing the modem on ebay and also dig in my past records to get the proof of my returning the original Comcast modem which I am sure I still have it.  They even denied to have record of my returning item.  I found this is outrageous for them to not only accusing their customer of buying stolen item but also of being a liar.  I used to highly regard their customer service as one of the top but not anymore after this incident.  They are now very rude, unprofessional, and show no respect or care for keeping the customer not mention their internet speed is extremely slow.