IIRC, years ago there was an EU directive forcing phone companies to separate service contracts and device payment plans. Network locking still exists, but unlock codes need to be free after you've paid off the phone. This leads to a situation here (Ireland) where some people are billed monthly for their phone itself, but the have a pre-pay plan on the sim card inside.

I thought the US had made a similar change banning that kind of co-mingling of charges.