Self driving is not a service, it is a feature of the car.
If it’s optional, is it really a feature? I know that’s a technical question, but a few years ago, when one got a car with a nav system, that was sometimes an optional purchase. Basically, it’s not that clear cut.
Maybe, or maybe not, self driving requires constant improvement and a herd of programmers continuing to serve the service and improve it.
Whatever it is, it’s been paid for, so you don’t just pull it from under my feet.
The price was decided upon purchase and unless it specifies limits it’s “lifetime”
It requires frequent patching and updates. I'd call that a service.