[Q] Please Read, need help unlocking n900T topic

Ok, so I purchased a used tmobile n900T which is no longer on a subscription. I want to put this phone on straight talk, this is what I have done so far:

1: Rooted using towel root

Attempted to unlock using the method explained here: http://forum.xda-developers.com/show....php?t=2471742

I did everything exactly as explained in the directions, but when I boot up using the AT&T Straight talk card, it asks me for a sim unlock code....

I went to one of the sim unlock websites: cellunlocker.net and the instructions told me I had to have the note 3 on a tmobile plan before I can get the unlock code?

any suggestions? thank you for your help.