internet order, Llc I ordered a 10$ CD and received an additional 2 CD's, and now they claim $500 from me philadelphia Pennsylvania

I ordered a 10$ french CD of the Pimsleur Approach, 18 months ago,  on internet for my girlfriend to learn my mother tongue. I did not pay attention that from this day on, they were still taking 64$/month from my credit card. After 30 days, they sent an additional CD, and then another one. Fortunately, i lost my credit card, and had to cancel it after Pimsleur paid themselves 128$.

I never saw the CD's because of an internal problem in my appartment complex. So, i did not take any action. 6 months ago, Pimsleur started sending me letters to claim the 384$ i "owe" them. i tried calling them, explain them the situation, but they refuse to hear what i said: I investigated at my appartments complx, and ended up finding my CD's.

i offered Pimsleur to return my unopened CD's in exchange with them waiving my "debt"! they told me it's my fault, that i agreed to the "terms and conditions of purchase", and that the upcoming CD's were mentioned clearly, as well as the rates. At the end, they rejected the return of the CD's, but they offered me a discount: i pay 300$ and we are good! I refused, because i feel i have been abused!

I tried calling them a few other times, but they never put me through to their manager, and they show me they're not scared of any lawsuit. they seem to have been trained. they seem to know exactly how to handle complaints. they're extremely rude!

since then, on may 1st, i received a letter to request my payment. I received a new one on june 1st, threatening me to go to take more drastic collection actions. should i pay them? what should i fear if i dont?