Can I buy an iPhone off eBay locked to another network and get it unlocked to O2?

[BuzzLiteYear]

I'm buying a second hand phone off eBay for my daughter and want to get it as cheap as possible but in good condition.
My choice is much greater if I don't restrict myself to unlocked phones or those already on O2.
Is it easy to get an iPhone unlocked?
Thanks

I've literally just had the same scenario. I think it's easy enough for all networks except Vodafone.... this is the one I was trying to unlock 🙄🙄😂😂

Thanks JoJo, how do you do it, take it to a shop or contact the network?
How much does it cost?

You can take it to a shop and pay or call the provider direct usually for free. Actually online too I believe. Just don't get a Vodafone one!!!

Also if you haven't already got a sim, Virgin ones are excellent value.

I need to go with O2 (Giffgaff) as Virgin wouldn't have any coverage where I go on holiday on a regular basis.