Bait and switch with cheaper product

On July 13, 2009, I ordered twenty (20) Hydrion pH pencils, which look like normal pencils, with about 7" of usable pH material. I was charged a total of $596.41 ($28.46 per pencil plus $27.21 for shipping) using my credit card. Sciencelab.com received the money on the same day. On 7/14, I received a notice that the product was backordered, and should arrive within 10 business days. On 8/3 and 8/13, I requested an update. They replied on 8/14, the products would ship that day. On 8/20, I received a shipment from them, but the items were wrong. They shipped 20 mechanical-type pencils instead of the conventional pencil-type that I ordered. The mechanical pencils have less than 1.5" of usable pH material, compared to the 7.0" of usable material that the conventional pencil has. The mechanical type of pH pencil can be purchased elsewhere for around $10 per pencil, much cheaper than the ones I ordered. I immediately sent an email on 8/20 notifying them of the error and tried to call them several times on 8/21, but no one answered. I sent another email on 8/23 but again no reply. I sent a third email on 8/27. Finally I received a reply, but it just informed me that the conventional pH pencils were discontinued, so they sent me the mechanical ones instead. Since I did not order the mechanical pH pencils and I did not agree to purchase or accept the mechanical pH pencils, I asked by email for a full refund on 8/27 and again on 8/31. Sciencelab.com again ignored my requests. I sent another email on 9/4 in which I threatened to file a claim with you if I did not hear from them with a fair resolution by 9/9. At last I received their reply on 9/8 in which they insist that I received my order in full and they will not issue a refund. Sciencelab.com charge me $28.46 per pencil for ones that are worth less than $10 per pencil and provide less than 1.5" of usable pH material rather than the 7" ones I ordered. They did so without my agreement and insist that I have to accept it. I think this is fraud and theft.