No one says subscribe from to mean unsubscribe. I tried to make it make sense, but it’s too much work to understand when no one says it, and everyone calls it unsubscribe. To subscribe is to scribe your name, sub (at the bottom) of a document. That is, to enter the subscription agreement. You don’t sign a new agreement to exit the previous one, you just exit it (stop paying). You undo the contract, you don’t pay and they don’t give service, we say you unsubscribe.