This must be bruted accounts. It supposed to be used as account sharing.
Whey you will add any IP address to favorites or change password then the access to VPN will be immediately restored ty the original owner. Considering that it is free data and you are far not the only one who is using it then you will lose this acc pretty fast (if it works at all).
i don't know if the website is sharing a bruted accounts, but i know most of these vpns support account sharing up to 5+

for me it is working i just dont change passwords