Received a media file from this number on whats app chat window. On asking whose number is this got a reply, "


Thanks for your interest. We will get back to you. This is a fixed response.Do not reply.
Transaction: 2423341120097464320

2014-07-08 11:58:37"

There is a very good possibly that you will find a charge on your next phone bill.  If you don't know the number never call it back.  They may attempt to bill you every month as well.  I would call your carrier up right away and find out if they can help you, otherwise you may end up being stuck for any charges.