Ebay are very strict about exchanging contact information with other members and would have given you a warning before you sent the message.
You are lucky it was only a 3 day ban as some members have been permanently banned.
Ebay says the potential buyer has to buy the item but not pay for it until they have attended and viewed it. Then, if they are happy they can pay and take it away, or decline it and seller does a mutual cancellation.
