The WanWay S20 is a popular GPS tracker frequently sold on Amazon at a great discount (sometimes even less than €10).
It comes with a SIM card already installed, which seems to be provided by Vodafone NL and uses 'internet4gd.gdsp' as the default APN. Unfortunately, to use this SIM card, you have to purchase a subscription plan and use the "TrackerOne" app, essentially giving your live GPS location to a Chinese server.
Luckily, with some tricks, you can fully unlock this device and use it with your own SIM card and Traccar server by following these steps.