I'm against the idea of using free VPN service.
In order to offer high quality services, VPN providers have to pay considerable amount for the  bandwidth and it makes it hard to find a reliable service with for free.  While you search for a free VPN service please note that such Providers  are more likely to log your activities and serve contextual ads while  you're connected. They're also more likely to use your usage habits to  tailor future ads to you, have fewer exit locations, and weak  commitments to privacy so if logging and privacy are important to you,  you may want to avoid them.
In order to find the best one, go online and check out the reviews for different VPN services. Make a comparison of the features, costs,  security, speed, bandwidth, server location and connectivity protocol.  By doing your research beforehand, you can narrow down your options to  two or three VPN service providers before making a final decision.
I personally subscribed to 
purevpn and it's so far so good however you can find more similar providers by looking for it in Google.