Can a collection agency pursue collections w/o providing me the original amt. turned into collections as well as where the acct. originated ?

The account was from a credit card that i activated approx 8 yrs ago. It had monthly fees. I never used the card but payed the monthly fees for approx 6 months. I then called them and told them I no longer wanted the card and to cancel theacct. I never heard anything from them after that. Now all this time later I get a letter from a collection agency saying I owe$787 and if I pay within 45 days that they will accept $157 . When I calld them for information he couldnt provide me with the original amt. turned into collection or how long it had been in collections before his company bought it from another. Im not sure how I owed anything on a card that was cancelled and how I went so many years without hearing from them if I owed them. Now they put thistime limit on me and I feel like if I take time to fnd out my rights I will be forced to pay the high amt on something I dont feel I owe. They even pulled my credit report as a way to find me. If they could why didnt the original creditor