Same in the UK, we change providers every few years depending on what deals are available. BT generally owns the last mile but is required to share it with other providers, then there are regional cable and fiber networks. I do believe in the power of markets, but as Adam Smith pointed out they must be regulated in order to be free and fair.
Who owns the wires?
British Telecom. Most of the infra was laid down when it was a government owned monopoly. When it was privatized and the ownership went into (mostly) private hands, it was required to lease out access to competing networks. I understand several other European countries have similar arrangements. In the UK we have the same for electricity and other utility provision as well. It's not ideal, but seems to work ok and has genuinely driven down prices for consumers a lot.