In fact, your IP address does not change. Moreover, the Internet provider is nothing like deceived. The ISP can "see" that you have connected to the VPN server. Yes, the data stream will be encoded, so the ISP will not tell which sites you visited after that. It's just that other participants in the communication will see the address provided by the VPN server as if it were your address. Until you disconnect from the VPN server, all your connections will be rerouted as if you and your provider were where the VPN server is. Only VPNs having multiple servers in different locations allow you to select a region by further redirection. As soon as you disconnect from the VPN server, the encoding disappears, and your ISP gains access to your unencrypted traffic again.