Imperial Collection Services has contaced me RE debt with Bank of America (credit card) for $7476.77. I disputed the debt within the 30 days allowed by certified mail with return signature. In the letter, I specifically stated that they cannot add interest or fees to the amount of the debt. Today, I received a letter from them stating that I have failed to respond to their previous notice and the balance is now $7,621.42. HELP. How should I proceed next? Should I write them back and let them know that I disputed the debt within the 30 days? These people are really aggressive.