? That doesn't make sense. There is no charge for being a seller. Only the selling fee when you sell something.
I've been buying and selling on GB for 8 years and never sent an email asking for money. They charge your listed credit card for their fee after you sell an item.
Apparantly there is a monthly fee if you register as a seller or have posted items for sale. Other people tell me that they pay two dollars a month and I'm not imagining that they asked for the money, I'm tell you they demanded it or they would freeze my account. They wanted my credit card number to charge the fee to. I never had to give them my credit card number for the first five years I joined GB and saw no need for a non seller to have to give them that info. This wasn't a phishing email, it happened on their site and they did indeed freeze my account when I wouldn't give them the card info and agree to pay a monthly fee.