I bought an unlock code from http://www.unlockcode4u.com because my phone was asking for it (Enter PIN Code)

I got the code and it does not work. Actually only allow me to enter 4 digits. 
Now this guys are telling that the code is for the phone's "Network unlock" not the "SIM unlock" and if I don't remember the PIN I will need to the PUK code from my network provider, so I feel that I paid for something I don't need.

This is the first time I try to do this and I feel frustrated.

I would really appreciated any help.

John