I received a notice in the mail from a law firm that was hired by portfolio recovery services stating that i a?

stating that i am being sued for a credit card debt, I wasn't served, but this notice came from the circuit court. My court date is on May 9th. They are stating that i owe 2500, but the original credit limit on the card was 1500, and my total before i stopped paying, when i lost my job, was 1400. So i need to know if i can call the law firm now and try to settle out of court, for less than the 2500, or is it too late. A process server did come to my door, but i was not home and was not served, so does this notice serve the purpose of service? Also, in the envelop was another law suit for an unrelated person to me, obviously placed in the envelop in error. Does this other person have any recourse against the law firm, since i now have their personal information? How do i handle that too? Should I tell the attorney of the error when i call them, or will they not care at all? Also, I live in Wisconsin if that matters in the answer. I am not denying the debt, just the amount. Thank you for your help!