The code isn't your phone code, its a sim lock code. If you enter it wrong to many times you will lock the sim up and then you will be asked for a PUK code. You have to ring your supplier for this. Maybe you will be able to ask them but i fear that if you cant remember it then your stuffed until xs++ is able to use db3150 handsets.
HOWEVER once you have your PUK code it never changes so no matter how many times you lock your phone up you can unlock it with same PUK code.
You have a minimum of 4 numbers with countless combinations so get thinking!!!!!
Lav