I have a sony ericsson Z310i cell -phone bought from the UK, but has t-mobile sim in it. I am in Ghana and will like to use it here. How can I get the code to unlock it?

Ring the service provider, if the phones not registered to you though then say good bye to it as they will completely block it.

Unlocking a mobile is very easy nowadaya. U can unlock it by service provider or from the online itself. I found the unlock free codes for Nokia,lg,Samsung from Unlock-Free.com : Unlock your mobile phone for free