How do you unlock a Nokia 1800?

I bought a phone from Phones4U specifically for travelling. The guy at the desk said it was possible to unlock it and to go to a shop round the corner to get it done. I went to 3 seperate places, none can unlock it and i can't find anywhere on the internet that can do it. I tried to take the phone back and they said they cannot give me a refund or exchange. Slightly annoyed!

Does anyone know how i can unlock this phone as i am stuck with it now!!
Thanks everyone for your answers so far, but these websites cannot unlock my phone for me. Once you click on the options it tells you that they cannot unlock Nokia 1800....
Thanks everyone for your answers so far, but these websites cannot unlock my phone for me. Once you click on the options it tells you that they cannot unlock Nokia 1800.... 'We currently do not have any unlocking services that are supported by your mobile phone.'

You need to mention your network too. Anyway, You can visit http://www.simpleunlocking.com/nokia-1800/rs16wp9/ to get the unlock code for your Nokia 1800. This site gives unlock code for a wide range of networks. All the best mate.