I've thought of ditching my godaddy account for this very reason. If i'm searching for lots of different domains it automatically ticks some of them and adds to your cart. I nearly bought one by mistake the other day, but notice at the last moment. And then a day later they added on for £4000+ to my cart. I think this is very sneaky behaviour on their part. It is so easy not to notice. You check one domain and realise it's not availaible, you don't notice they have added a $4K domain to your cart, then you find and buy another one. You don't bother looking at the cart properly because you only expect the domain you picked to be there. Yes, you should check, but this is disgraceful behaviour. Other companies don't add things to your cart just because you view the product. Behaviour like this should be made illegal.
Show the credit card company how this sneaky behaviour works. Or take them to court. They may back down because they won't want the bad publicity.