with whom your contract (to purchase) existed. Tell them that you are rejecting the player as not fit for its purpose, and that you want a refund - or another brand of player that is equal to, or better than the Creative Muvo in terms of specification.
You may choose to accept a replacement of course, but perhaps the same thing might happen?
Ebuyer will want to examine the item before they take any action. Make sure you confirm your rejection in writing - this is very important.