Magellan RX Billed me for 2 years even when I had private insurance and now trying to collect $688 philadelphia PA

Magellan signed me up for a Medicare part D premium for prescriptions. I stopped paying the $30 some dollars a month because I got my own private insurance that covered prescriptions in 2018 from my full-time employer. Magellan is NOT a part of Medicare. They are a private company. They continued to send me an invoice but I threw it away each month figuring they would cancel since I had not paid them as ALL insurance companies do this if you do not pay.  Had I KNOWN they would continue to bill me, I would have ended it.  Now they say because I did not contact them I owe despite I was paying, and using, my own private insurance for prescriptions through my employer. 

I NEVER once used their policy to pay for even one prescription and was under the impression I no longer had NOR did I want this coverage as I already had prescription drug coverage through my employer in which I worked full time.

Finally, I opened one of their pieces of mail wondering why they still continued to send these to me. And they had me with an accumulated bill of $668.70!!! I wrote and was told to simply tell them I need to retroactively disenroll to Jan 2018 when I had signed up for my own work-related insurance and provided them a copy of my insurance card. I faxed this information now to them twice over the past year and they STILL continue to bill me. I am requesting this be eliminated as they said they would, and Medicare has stated this is NOT them and this outfit (I see as a scam) is a private entity.

What they have done is at the very least unethical and dirty.  I’ve seen the exact same complaint on the BBB website so they know what they are doing and know it is WRONG.