Recently I upgraded my 2 phones. My original service provider was AT&T Wireless, but as it has been acquired by Cingular, and also because my 2-year contract was over, I choosed to upgrade my phones. I upgraded my phones thru my employer so I got a really good deal (my company has agreement with Cingular, so Cingular gives special discount to corporate users) from Cingular. I selected 550 min rollover shareable minutes with FamilyTalk for the two lines. For the phones, I selected Cingular 8125 SmartPhone (Windows Mobile 5.0 -based) and Nokia 6102 (camera is built-in).
After activation, my old phones were not working anymore, even if I swapped the old SIM card with the new one. But, thanks to http://unlock.nokiafree.org/, I was able to unlock both phones and now they are working fine with new Cingular SIM cards (and, hopefully, with any SIM cards around the world). I am still having diffifculty to unlock my Cingular 8125, though. Eventhough I found a website that gives unlock service (http://www.imei-check.co.uk/m3000unlock.php), but it is ridiculously expensive ($38), and I don't trust the site yet. Anybody can point me to a free unlock tool as unlock.nokiafree.org?