Orange will not unlock the phone for you unless your the original owner and your account is upto date, trust me I tried, told them I bought the phone second hand and they told me they won't unlock it unless the previous owner does it, no get around your stuck with the network.

So to the seller, get them unlocked before you sell them if you want to get rid, because whoever you sell them to wont be able to. Orange say 28 days but I've done loads and it takes about a week, unless there's another reason why you can't unlock it yourself????