They do both.

When I bought my car in 2015 it came with the free trial but I specifically did not sign up for a subscription. When the trial ran out they started hounding me and I basically struck a deal: I'll get a year subscription but if and only if you invoice me. Mail me a bill in the mail and I will write you a check and mail it to you or make a one time payment on your site. No auto-enrollment.

The first two years they did this no problem. The third year they put up a big fuss and told me that wasn't something that was possible. I asked how it was possible for the past two years and he said I must have misunderstood. So I said okay, if that's not possible then I guess I'm done with Sirius and hung up. A few days later I got another email and called in again and asked that rep for the invoice option and she said while it's not commonly done, she'd make an exception for me.

The year after that I tried three different reps and nobody would invoice me so I cancelled and haven't signed up since. They still sent me mail and email for years, and somehow they fucked up their database and when my parents bought their car (same make, different model) now I'm getting all of their ad email from Sirius again, but they did stop (intentionally) emailing me after about two years of no contact.