Using a VPN to hide usage while tethering g flex ??

Hey guys needing a little help and as pretty much as the title states I'm needing help setting up a VPN on my G flex I have a d 950 unlocked and I'm using it on metro pcs. Problem is I can't find a VPN that will work or a tether app that will block usage like foxfi would. But being that I can't get foxfi to work and the only app i can get to work on my g flex is "wifi tether router" I need other alternatives . Or a good vpn that will work with our phones and or settings can anyone help?