VPN-network is one of the most useful technologies that we have when it comes to protecting your privacy on the Internet, because they can encrypt your data and change your location. Unfortunately, premium services of these services often cost money.
What's the catch? For the services of any free service, you still have to pay in one way or another. Maybe you can exchange a limited amount of data. Maybe your connection will be very slow (in other words, no Netflix). In the worst case scenario, encryption of your data will be unreliable, you will be overwhelmed with targeted advertising, and your confidentiality will be under threat. Free VPN services are perfect for occasional use of the "from time to time" model, if you need to encrypt your data - for example, when connecting to an unprotected network.
In general, I will always use paid VPN.