Note: This process will only work with a Jailbroken iPhone and there is a registration fee of 4.99€ to use Guizmovpn (you can test it for free during 7 days).
First of all we need to install Guizmovpn via Cydia. This is perfectly explained in Guizmovpn site, so just follow these easy steps.
Once we have it installed, we start the configuration process.
First we execute Guizmovpn.
Execute Guizmovpn
We click on Download new configuration and we choose Other in the VPN providers list.

Download Configuration
Now we type the URL from which we will download TUVPN's Guizmovpn configuration and click Yes when asked to download:
www.tuvpn.com/downloads/tuvpn_guizmovpn.zip
Download Configuration
That's it! TUVPN should now appear under the configurations list.
Configuration Installed
Select it an click on the OFF button to start the connection process. You will be asked for your TUVPN VPN Username and Password that were sent to you in your Service Activation email. Click Save and credentials will be stored in your iPhone.
Connect VPN
And you are now connected to TUVPN!. You will see it with the Guizmovpn icon on the top bar next to your battery icon.

Connected
But, let's check it with whatsmyipaddress.com!
So you see that we are connected to our Erfurt (Germany) server.

Check Connection
You can very easily change the server you want to connect to. From the main Guizmovpn screen, click on the arrow next to the tuvpn_guizmovpn configuration. And then you will see two tabs at the bottom: Settings and Editor. Choose Editor.
You will get to OpenVPN configuration file. Simply change the vpn server name to the desired VPN Server that you want to connect and click Save. Next time you connect you will be doing it to the new server!
Change VPN Server
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