Unlocking nokia 3120 classic

Hi, I just need a few questions answered. My sister got 2 free nokia 3120 classics from work but they're locked to the O2 network. We're both Meteor and want to remain so and have been looking around for places to get the phones unlocked. I'm completely clueless when it comes to phones, but came across a few threads online dating from last year, saying that this phone cannot be unlocked.. Went into a shop in Navan and the guy said he'd do both phones for 50euro. I was told you could get this done for a tenner on Moore Street.. Assumed he was trying to scam me and told him as much.

So I just need to know if this phone (which is actually not even as good as my present phone, but I want it anyway) can be unlocked, and if so, how much should the service cost me? Also if anybody could suggest a good place on Moore Street that would be great!

Thanks