My son has a Sony-Ericsson z525a and will be using it when he travels to
Spain next month.  Cingular/AT&T has assured us that the phone has the right
frequencies to work overseas. We have decided to buy a Lebara Spanish SIM
card to use in the phone while he is overseas.  That will greatly reduce his
cost of making outgoing calls.

The phone is currently locked, but Cingular gave me the unlock code and a
procedure to follow in doing the unlock.  My question about the procedure is
that it says to remove the Cingular SIM card and put in the new SIM card
BEFORE doing the unlock commands.  Does this mean you can't unlock the phone
while the Cingular SIM is still in it?  Or is there some other reason they
said to do it this way?

The procedure they gave me is the following:

1) Power off device and remove AT&T SIM card.
2) Insert SIM card from another wireless carrier.
3) Power on the handset.
4) Press the Left Arrow (<) button.
5) Press the star (*) button twice.
6) Press the Left Arrow (<) button.
 - display indicates "ME Lock"
 - wait approximately 3 seconds.
 - the display indicates "Network" and a picture of a closed lock.
7) Press Yes.
 - the display indicates "Unlock?"
8) Press Yes.
 - the display indicates "Enter NCK"
9) Enter the SIM Unlock code.
10) Press Yes.
11) The handset displays "Network" and a picture of an open lock for three
seconds and then reverts to the main display.  The handset is successfully
unlocked.