David Efron wrote to confirm the Cingular handset unlock policy that we documented back in April:
I had an exasperating set of phone calls with Cingular which finally ended in confirming what you posted regarding the unlock policy. Domestic-only phones have locks, to prevent abuse of the carrier. They claim that any phone with 900 and 1800 bands will work when a foreign local carrier’s SIM is inserted. The agent sent me a paragraph from their internal system confirming that fact, reproduced below:
All currently available GSM and GPRS devices that contain at least one International Frequency (900 MHz or 1800 MHz) are not locked. This means a customer can insert another SIM into these devices, for example a pre-paid SIM from a foreign carrier. If a customer does this, they will no longer be reachable at their Cingular number and charges will not appear on the customer’s Cingular bill.
T-Mobile, however, from which I switched, told me that their phones, even dual and tri/quad band, have to be unlocked, but that they would email the unlock codes on request, and that on return to the US the phone would remain unlocked with no need to re-lock it.
Thanks, David, for sharing your experiences with Cingular and T-Mobile with us.