Hello Mr S,
Do you mean the last three digits appeared in the back of your credit card?
Many (if not all) online merchants require you to put those numbers to validate your transaction. I had experience buying things online from us.harp.com and some music online using credit card and so far it didn’t give me any trouble at all. Usually those sites have policy about buyer’s privacy. Please check if they have statement about it.
I suggest you to change your question if there anybody in this site that had experience with the company you mentioned above, that will give you more accurate information about the company’s reputation.
Good luck with your purchase..
Bowie