I have unlocked my T-Mobile 8320 (by calling them) and verified that the SIM Network setting says "disabled". However, when trying to use this phone with other SIM cards, it doesn't work. The specific country that I am attempting to use the phone in is Ukraine, which uses 900/1800Mhz frequencies. Is there some other setting on the phone that needs to be changed in order to allow the new SIM to be used?