I cancelled my Molina Health Insurance through the Marketplace successfully and Molina refunded me, because I am currently working part-time. I always paid my monthy payments in full and never had any medical problems. Since the time of cancellation, I have received two threatening letters from this company/collections called AGS in Sunrise-FL stating they represent a client who states I owe $400 for a pre-med screening, and they would be willing to settle for $280. Do I ignore these letters, do I tell them to no longer contact me, will they ruin my credit further, or is this a scam/medical fraud ?