I completely agree. This is their core business: they know very well what to do so that people don't cancel (keep quiet, not send a reminder), they know equally

I completely agree. This is their core business: they know very well what to do so that people don't cancel (keep quiet, not send a reminder), they know equally well the percentage of people who will get mad, they know how small the group is, and that the net benefit is well worth it. I don't think one chargeback changes anything, but if people are more aware (not just in case of LinkedIn, but in general), this could make this shady business strategy less profitable.