VPN service on IOS is very hard to find especially if you are finding free VPN service.
I think it would be easy to find those kinds of VPN’s but it would be easier for hackers or the VPN providers to track and sell information about you. It’s hard to trust free stuff.
I recently obtained a Premium for my account in a Password Manager. It offers VPN when you are subscribed to a yearly payment to them. Ever since I have not encountered any problems with it. I’m currently using it in my desktop and mobile. Maybe you guys would be interested in those kinds of offers that are available.