Fighting robocollections

So, I’ve just mailed my answer to a suit by a big bank in , I think, Orlando, for a measly $2000. We were doing fine for several years, and all of a sudden they reduced my available credit and then just as suddenly closed the account. It’s a store card.

My argument is that I only once heard from a human being at the bank. Even the certified letter was unsigned. The preceding and succeeding phone calls were unidentified and prerecorded, requiring me to take down a different number to call, prove my identity, and “make arrangements.” When a human did call, they knew nothing about me but my balance due.

Has anyone else tried this argument? Any advice?