If a message or reply you received from a seller had profane language, racial. religious, or ethnic slurs in it, it can be reported by using the Action box drop down menu just above the message when you open it to report it, and you can also use the Block this member option to stop receiving messages from them.
However, unless the message had one of the above mentioned type of words or terms in it, ebay will not take action. If you did not buy anything from the seller there is no other actions you can take. If the message was about an issue with a purchase, then open the appropriate dispute for the transaction, and/or leave appropriate feedback for the seller mentioning the reply, and give them a 1 star communication rating.
