By "block" do you mean it's asking your for a password after the Tmobile page (before android starts)?
If so, you have enabled the "Secure startup". There is no way to jump this part. you have to input the correct password for android to unlock itself and use the phone.
If you don't remember the password, then recommended you go to a BestBuy store with the Samsung kiosk so they can see if they can reset the phone.
Or do you mean "Blocked" as in cannot be activated on any network? You might want to try the IMEI in the T-Mobile IMEI checker to see if 1.) The device has ever been reported lost or stolen or 2.) It still has a lien on it, as in whomever sold the phone was making payments on it but something has gone awry with the account and they are no longer making payments.
Using the IMEI checker can help give us a good idea as to why it was blocked. Have you entered your IMEI in that system to see what it says?