How can I unlock my D750i phone for free?

Question

It is currently a T-Mobile and I want it to be an O2 thanks.

Answer 1

Here is your link
http://www.foneszone.co.uk/cable_unlock_here/SonyEricsson/D750i.php

and
http://www.gsmliberty.net/shop/sony-ericsson-d750i-instant-remote-unlock-p-615.html

Answer 2

call the cell phone company and have them unlock it. the auto default is usually the last 4 digits of you phone #. If you are trying to carry your phone to a new company its not going to work. you can port your old number in as long as you do it while you are active on your current carrier, but the phone itself isn't going to work with a new carrier. hope it helped.