I'm connecting using VPNBook servers and it works fine with this command:
sudo openvpn --config /etc/openvpn/vpnbook-udp-53.ovpn --auth-user-pass /etc/openvpn/password.txt
but I just can't seem to figure out how to stop it without a reboot.
service openvpn stop and
/etc/init.d/vpnbook stop, but that doesn't seem to affect it.