Well, you can use it, but the free proxy apps are not secure and you are never sure that it does not keep your logs. Moreover, after a while of use you are asked to update for more features and that requires payment of some amount. So, it is better in the first place to use a paid premium vpn which also allows you to use multi-logins which means with one account you can use it on 4-5 different devices. They are more secure and also provide support to the customers, if anything goes wrong. Free ones are filled with ads too.