The buyer used your computer and your cc to purchase an item you didn't order and sent it to a different address?
And the seller didn't cancel the order, because he thought you were just making an excuse to cancel, not that it's not your order at all.
I would worry. First I would check with everyone in my household to see if they made the order. Do you know the shipping address?
I know this is a late response..
The buyer used my account, but I don't know how they paid for it, none of my payment methods,
And they added a new shipping address, one that I don't know