In the sense of unlimited use, there's no such thing as a free VPN. If you're tech-savvy, the best thing to do is rent a low-cost Linux server and set up your own VPN, which will cost you around $25 to $40 per year depending on where you'll be renting the server.
But there are many free VPN providers in Google Play.
It's easy to download any VPN.
Basically, most VPN providers will offer you the opportunity to try their VPNs, but at first it's slow and the lines are few. Later, after you've downloaded and used it for a while, they'll recommend that you purchase their VIP to get faster internet. Typically, you will spend $20-30 per year. It's really not very expensive. However, if you want a more cost-effective VPN, I can recommend ShellVPN.
There are currently several forms of free-of-charge:

  • Limited traffic free, 300M per month

It's limited. It's probably not enough.

  • Watch ads free trial

Time consumed watching ads can be more expensive.

  • Invite a friend for time

Not so many friend invitations, trouble.

Free VPNs that are advertised for free are generally not secure. Remember, if you don't pay for the product, then you are the product, and they will sell your data to anyone who pays. You definitely don't want a VPN provider to sell your data.

And ShellVPN is cheap, no ads, no invitation, unlimited speed, up to 100Mbps!
That's why I'm so obsessed with this VPN. It provides quality services to its users in an innovative way.
Sign up during the ShellVPN beta test and get 1 months of free use.