I had a similar experience- defective cartridge, no customer service. I filed a complaint through Better Business Bureau, and TFP's response was totally pathetic.
According to their own warranty info, the customer cannot return a defective cartridge until they get authorization (after emailing them).
Their response to my complaint was that I never mailed them the defective item. Well, no sh*t. They never sent me the authorization in the first place, as per their own policy (and which is required).
Anyway, instead of wasting any more time with these losers, I'll just recommend that you buy from a more established company such as Staples, Officemax, Wal-Mart, etc.
TFP ink is a scam- they've got negative reviews everywhere- I only wish I had known about it sooner.