Hi guys

I've been searching through all the threads about unlocking 6600s, and wonder if you could just please clear it all up for me as I'm still a bit confused.
It's for a friend's phone so of course, I don't want to go messing it up and having to pay anything for when he has to take it to a shop!

OK, I've found advice such as use code 2 and 5 (but is this just on Orange?)
I've found try 1, 2 or 5, but not 7, then conflicting advice to try 7.

If it helps, it's currently on T-Mobile (UK). I have downloaded the v3.10 calc.

Thank in advance.