It's a really weird problem to have, I've had it in one of my products. Someone signed up and I was super happy to have a paying subscription. The first month or so I could see they hadn't yet made use of the service. No worries, maybe they just hadn't got around to it. Couple more months, still no use, what to do? Could it be fraud, but how does that work? No one gets anything from me, and I get all the money?

Do I cancel their subscription? Is that the right thing to do from a customer service perspective? I have no idea. Sending an email that says "Hey, um, did you do this accidentally?" is a bit unprofessional. I tried contacting them to no avail, to see if they needed help setting up to keep it professional but still remind them they have this recurring subscription they might not want. Eventually I ended their subscription and left a professional sounding "We noticed you're not using our service, so we have paused your subscription." email and ended it.

I still sometimes wonder if it wasn't a friend or friendly stranger who wanted to support me, and if it was I must sincerely thank them.