[jraph]

There's also the simlocking.

In France, (many/all?) phones bought from the carriers (with a subscription with some time commitment) were (are?) simlocked, meaning that they could only accept SIMs from these carriers. But carriers are also forced by law to let you sim-unlock your phone for free after a few months. So yes, pretty seamless and common indeed. Everybody expects to be able to switch carriers and keep their phones.