This scam is horrible. I currently work for a shopping cart developer and I used to do technical support for Symantec (Norton AntiVirus). I'm glad you took steps to remove the link from your store though; I personally would have terminated my account with the company. There are enough competitors on the market that you shouldn't have to put up with a business that operates this way.
While I don't want to come off a salesman, I don't want internet ecommerce to perpetuate this type of scamming either so, I've included below a list of other shopping cart options.
Free shopping cart options:
Zen Cart
Oscommerce
Cube Cart
Fee based shopping cart options:
Volusion
Monster Commerce
Modular Merchant (I work for this company)