First you need to find out what's your phone CID.
Then if its CID52, its easy unlock. The Unlocking Process is bit hard.
If its CID53 then its a bit of no confusion !!!You will need bypass package for the firmware in your phone.
Flash S500 to w580
Unlock db2020
Any CID patching
Sony Ericsson db2020 patching
free unlocking db2020 sony ericsson
thx bro......