Unrefunded credit for returned product

On 11/9/2008 I bought a refill for HP printer/fax.  The product was HPC6658 (PN IJDC6658R). When I tried to install the cartridge, it will not insert in the slot. After comparing the configuration of the old cartridge with the ordered one, I found out that they used the cartridge for the black ink instead of the colored one. The cartridge has a tab the prevents it from sliding into to the color cartridgeslot.  I returned the product as instructed in their website on 11/23.   I have called and left a message on 12/19/08 and e-mailed them twice on 12/5/08 and 12/26/08 to request for an update. To date (approx. 5 weeks since the product was returned), I have not received any response nor a credit for this returned product.