Wrongly persecuted by credit card company

I had a credit card with Consumer's Edge, which was then bought out by Chase. I believed that the rate was fixed, but had lost my copy of the original contract.
In July 2000, Chase sent me a notice that it would be raising my interest rate. Since I believed that the rate was fixed, I requested that Chase verify the validity of the rate-hike by sending me a copy of my original contract with Consumer's Edge, and showing me where in the contract that this was authorized.

Chase failed to comply with this request within 30 days, and so I repeated the request several times over the next six months, telling Chase, both by telephone and in writing, that I refused to make payments on the account until this rate-hike was verified; Chase failed to comply each time, but simply continued to bill me as if I had said nothing.

Finally in January of 2001, I faxed Chase a settlement offer, asking them a) to either provide a valid copy of my original contract with Consumer's Edge, or else b) I would assume the entire debt settled on the grounds of both wrongful unilateral contract-alteration, as well as lack of a valid writ to a debt by a third party (which is required for collection in Michigan).

Chase ignored the letter, but simply treated the account as delinquent, continuing to harass me with bills, threatening letters, phone-calls and collection agents, refusing to deal with me in good faith under the law.
Consequently, I have this debt listed in my credit report as a charged-off negative credit item against me for the amount of $1,500.00

I would like to get an official legal opinion as to my rights in this matter, and what would be my cheapest alternative.