Two days ago I received a phone call from a US collection agency based in California informing me that I have unpaid debt of $2800 U.S. from a business assistance company I was involved with four years ago. I subscribed to their services but after a short time I realized that their services were worthless so I canceled. I was quite sure all "loose ends" were taken care of but apparently not. How much damage can a collection agency cause in this case to a Canadian Citizen?