My gut would say it's not really your responsibility to prompt the cancellation as long as you're not actively trying to make it hard to do. That is, in this situation you'd be accountable but not responsible.
On the flip side, as a consumer, doing something like automatically pausing a subscription if it's not actively being used would make me think highly of your company
On the flip side, as a consumer, doing something like automatically pausing a subscription if it's not actively being used would make me think highly of your company