They claim you can use WireGuard and OpenVpn and IKEv2 - I’d opt for WireGuard.
So: you did not actually use it? 
maybe - it appears the documentation on how to make it work is somewhat lacking
Here:
they don’t even mention Linux.
same here:
I’d have downloaded and looked at it - but at this point I wouldn’t even know which one to choose.
You cannot change your IP - the best you can do is reconnect and hope you get another one from your provider.
… which is equivalent to not having changed it at all …
There is an AUR package last updated 6 years ago.
How did you install it?
And which one? The choice they give you is only between Mac, iOS, Windows and Android.
I have used Mullvad, then I got greedy and switched to AtlasVPN - but they soon closed shop and transferred all their users to NordVPN, where I’m now.
I’d not have chosen that one had I seen this coming - but I paid AtlasVPN for 3 years and that is how long I’ll stay with Nord before I go back to Mullvad. 