Do an internet search, generally the unlocking code is generated based on the IMEI that you can find in a sticker under the battery, and you can also get it with a given key combination. There should be code generators on the internet.
In Spain, lots of chinese and turkish-run business will unlock any phone for 6 euro or so. Basicly the final decision depends on how much the time it takes to find the code on the internet is worth for you.