Cellesim includes a free VPN with every active eSIM. It is not an add-on, a trial, or a paid upgrade: as long as you have an eSIM plan that is still valid, the VPN is available at no extra charge.
This is unusual in the travel eSIM market. Most providers sell data only, and you buy a VPN separately from a VPN company. A few bundle a paid VPN subscription. With Cellesim the data plan and the VPN come from the same purchase.
It matters because mobile data abroad does not solve everything. Public Wi-Fi in airports and hotels is unencrypted, some services are restricted depending on the country you are connected from, and banking apps behave differently on foreign networks. The VPN covers that part.