Past: N97, C905a, N85-3, N95-4, N95-3, k850i, v3xx, A1200 Ming
American Telephone and Telegraph
No. Debranding and Unlocking are two separate things.
Call your provider, tell them you will be travelling abroad and would like to be able to use a "native" prepaid SIM. They'll normally do this, but may require that you also unblock/enable the international roaming option on your own plan.. (usually no charge).