If you've ever unlocked a GD50 pls help

Hi,

I'd like to unlock my GD50 phone, I have already the codes (**5digits*8digits#) but can't do anything with them :-? . So if someone did successfully unlocked such a phone, please tell me how.
My problems:
- I have 10 codes which one do I need?
- If I enter one of theese codes nothing happens, the code stays on the display. If I now press the dial key it says "number not available" or something like that.
- Do I have to enter the code with a SIM inserted? (actually I tried both with and without a SIM)

I read some forums, but everywhere I just see "please unlock my phone", "your codes are:", but never "thx it worked". So I'm a bit confused now. If you can help me please do it.

thx in advance,
-tktEasy