All the major networks unlock any handsets they supply free of charge, or on payment of a minimal fee. There are sometimes qualifying conditions such as having had the contract for six months or not being in arrears on the contract, but for most folks they aren't onerous.
No tears shed for the passing of Phones4U (other than for most of 5,500 folks who'll lose their jobs) as some of their sales practises were decidedly sharp, if not downright dishonest - all just in my opinion of course...
JF