Unlocking mobile phones

I recently got a second mobile phone, and wanted to swap sims between the two.

The phones I wanted to unlock were a Nokia 6021, and a Nokia 6070

My experience was

• Get your IMEI code off your phone (type *#06# into the phone).
• Figure out if you are DCT3 or DCT 4 and your phone type from this site http://www.mobyproject.com/link/dct3&4list.txt
• Goto this site http://unlock.nokiafree.org. Enter the details and get the code
• Take out your sim and start phone without it.
• Type in the bottom (7th) code from the list following the instructions from http://unlock.nokiafree.org. (Press * multiple times to get letters *, P, W +)
  

Voila.

Of course there are risks.
This article gives a good synopsis of what to do and some exceptions that can occur
http://www.oreilly.com/pub/wlg/3935

Good luck