It was work car before and company installed GPS tracker with user authentication thru iButton / Dallas key 1-wire fob.
They sold it to you with car so you can use it, but you have to stop using sim card.
Most of these devices can have login credentials changed so you can use them with your own service or just open it and reprogram them.
OBD port can be for two things, only for power (most likely) but it can also send not only your position but speed etc. if that cable has two wires then it is power only, if it has more wires it can read other data from your car. On some cars it is even possible to apply brakes or other mischief ( but mostly US and chinese cars)