I received my order but the items were not as described.

If you received your order and the items were not in the condition stated in the item description, please try to resolve the problem with the seller first. E-Mail communication may be unreliable at times and it may be possible that the seller is not receiving your e-mails. If you do not get a reply to an e-mail, contact the seller using the My Messages system. Enter the order ID on the Contact Form and send the message. In your Outbox, you can later see whether or not the seller has read your message.
If you are unable to resolve the problem with the seller, you may then file a Non-Shipping Seller Alert and select the option "Seller listed items with error". This complaint can be filed if at least 7 days have passed from the order date. 
If the problem is not resolved within 2 weeks of submitting a NSS, you should Cancel the Order which will complete the complaint. If a seller has 3 orders cancelled via NSS, their store is shut down and their selling privileges are permanently revoked. If the problem is resolved, please remove the complaint on the same page where it was filed. If a NSS is filed and the seller contacts BrickLink with proof of shipping then the NSS will be removed.
Make sure to remember to post appropriate feedback when the transaction has been completed.