Work in the industry -- the reason you have to pay is that the companies do not contract with Verizon/ATT/Tmo to have always on connection unless you eat the cost. This is changing going forward due to the value of always on system monitoring (DTCs, oil change interval etc) to say you didn't do your part and the warranty is void, but that's not on stuff from the last 10 years and won't ever be. Also, current things don't benefit past the warranty period, which is why you have to pay beyond that point if you want e.g. remote start. This will change in the next couple of years with OTA updates and whatnot, but that's only now on Mercedes/BMW/etc and only just getting onto Ford/GM/Stellantis/etc.
My understanding of OnStar is that you have to disconnect some things to -truly- disable it. (Probably to let people 're-subscribe' if they try to use the thing when they aren't current customers.)
Other systems... I can say my Maverick lets you select whether to have vehicle location data shared or not, but TBH I don't trust opt-outs. [0] I've also run into the issue on my said car, where my opt-outs got de-opted when the dealer runs updates.
[0] - Also as a side note, I've had at least one loan note in the past (from a larger bank) where they stated a tracking device may be placed in the vehicle. Not sure whether they sell that data.
