Complaint Review: GSCM Collection

I received a letter as an "Urgent Notice: Debt Collection" for the amount of $39.97 and if the amount was not settled by 7/7/14 the new amount would be $59.97. This amount was for a product called Green Coffee Bean Max. I did give this "Green Coffee Bean Max " a try then cancelled after 1 month. I have not received any more bottles or a bill from them. My credit card also has not been charged from them as well. Although about 5 months ago, I received this exact same letter and just paid it because I have great credit and don't want to harm that. Here the letter came to me again and there is no contact information of a real person to talk to and dispute this. I am not sure want to do, as for now I have not paid this. I have read many other reports of this exact same thing happening to others. How will this affect me by not paying? Do I pay? This appears to be a scam and I paid them once already, dumb on my part.